Download as PDF, PPTX
![This is a talk about
1. how to actively read a new Python codebase
2. reading thru the python-requests codebase
“Indeed, the ratio of time spent reading versus
writing is well over 10 to 1. We are constantly
reading old code as part of the effort to write
new code. ...[Therefore,] making it easy to read
makes it easier to write.”
Robert C. Martin, Clean Code: A Handbook of Agile Software Craftsmanship](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-4-320.jpg)
![Goal for today —
Figure out how this code snippet works
>>> r = requests.get('https://api.github.com/
user', auth=('user', 'pass'))
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"type":"User"...'
>>> r.json()
{u'private_gists': 419, u'total_private_repos':
77}](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-9-320.jpg)
![httpbin’s /post/ endpoint is useful for testing requests
library
In [1]: import requests
In [2]: resp = requests.post('http://httpbin.org/post',
data={'name':'Susan'})
In [3]: resp.json()
Out[3]:
{u'args': {},
u'data': u'',
u'files': {},
u'form': {u'name': u'Susan'},
u'headers': {u'Accept': u'*/*',
u'Accept-Encoding': u'gzip, deflate',
u'Content-Length': u'10',
u'Content-Type': u'application/x-www-form-urlencoded',
u'Host': u'httpbin.org',
u'User-Agent': u'python-requests/2.9.1'},
u'json': None,
u'origin': u'50.148.141.36',
u'url': u'http://httpbin.org/post'}](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-27-320.jpg)
![Goal for today —
Figure out how this code snippet works
>>> r = requests.get('https://api.github.com/
user', auth=('user', 'pass'))
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"type":"User"...'
>>> r.json()
{u'private_gists': 419, u'total_private_repos':
77}](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-35-320.jpg)
![def request(method, url, **kwargs):
"""Constructs and sends a :class:`Request <Request>`.
:param method: method for the new :class:`Request` object.
:param url: URL for the new :class:`Request` object.
:param params: (optional) Dictionary or bytes to be sent in the query string for the :class:`Request`.
:param data: (optional) Dictionary, bytes, or file-like object to send in the body of the :class:`Request`.
:param json: (optional) json data to send in the body of the :class:`Request`.
:param headers: (optional) Dictionary of HTTP Headers to send with the :class:`Request`.
:param cookies: (optional) Dict or CookieJar object to send with the :class:`Request`.
:param files: (optional) Dictionary of ``'name': file-like-objects`` (or ``{'name': ('filename', fileobj)}``)
for multipart encoding upload.
:param auth: (optional) Auth tuple to enable Basic/Digest/Custom HTTP Auth.
:param timeout: (optional) How long to wait for the server to send data
before giving up, as a float, or a :ref:`(connect timeout, read
timeout) <timeouts>` tuple.
:type timeout: float or tuple
:param allow_redirects: (optional) Boolean. Set to True if POST/PUT/DELETE redirect following is allowed.
:type allow_redirects: bool
:param proxies: (optional) Dictionary mapping protocol to the URL of the proxy.
:param verify: (optional) whether the SSL cert will be verified. A CA_BUNDLE path can also be provided.
Defaults to ``True``.
:param stream: (optional) if ``False``, the response content will be immediately downloaded.
:param cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, ('cert', 'key') pair.
:return: :class:`Response <Response>` object
:rtype: requests.Response
Usage::
>>> import requests
>>> req = requests.request('GET', 'http://httpbin.org/get')
<Response [200]>
"""
# By using the 'with' statement we are sure the session is closed, thus we
# avoid leaving sockets open which can trigger a ResourceWarning in some
# cases, and look like a memory leak in others.
with sessions.Session() as session:
return session.request(method=method, url=url, **kwargs)
api.py
This is the request method](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-39-320.jpg)
![class Session(SessionRedirectMixin):
"""A Requests session.
Provides cookie persistence, connection-pooling, and configuration.
Basic Usage::
>>> import requests
>>> s = requests.Session()
>>> s.get('http://httpbin.org/get')
<Response [200]>
Or as a context manager::
>>> with requests.Session() as s:
>>> s.get('http://httpbin.org/get')
<Response [200]>
"""
__attrs__ = [
'headers', 'cookies', 'auth', 'proxies', 'hooks', 'params', 'verify',
'cert', 'prefetch', 'adapters', 'stream', 'trust_env',
'max_redirects',
]
def __init__(self):
#: A case-insensitive dictionary of headers to be sent on each
#: :class:`Request <Request>` sent from this
#: :class:`Session <Session>`.
self.headers = default_headers()
#: Default Authentication tuple or object to attach to
#: :class:`Request <Request>`.
self.auth = None
#: Dictionary mapping protocol or protocol and host to the URL of the proxy
#: (e.g. {'http': 'foo.bar:3128', 'http://host.name': 'foo.bar:4012'}) to
#: be used on each :class:`Request <Request>`.
self.proxies = {}
#: Event-handling hooks.
self.hooks = default_hooks()
#: Dictionary of querystring data to attach to each
#: :class:`Request <Request>`. The dictionary values may be lists for
#: representing multivalued query parameters.
self.params = {}
#: Stream response content default.
self.stream = False
#: SSL Verification default.
self.verify = True
#: SSL certificate default.
self.cert = None
….
sessions.py
R
eally
long
class
definition
of“Sessions”](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-41-320.jpg)
![class Request(RequestHooksMixin):
"""A user-created :class:`Request <Request>` object.
Used to prepare a :class:`PreparedRequest <PreparedRequest>`, which is sent to the server.
:param method: HTTP method to use.
:param url: URL to send.
:param headers: dictionary of headers to send.
:param files: dictionary of {filename: fileobject} files to multipart upload.
:param data: the body to attach to the request. If a dictionary is provided, form-encoding will take place.
:param json: json for the body to attach to the request (if files or data is not specified).
:param params: dictionary of URL parameters to append to the URL.
:param auth: Auth handler or (user, pass) tuple.
:param cookies: dictionary or CookieJar of cookies to attach to this request.
:param hooks: dictionary of callback hooks, for internal usage.
Usage::
>>> import requests
>>> req = requests.Request('GET', 'http://httpbin.org/get')
>>> req.prepare()
<PreparedRequest [GET]>
"""
def __init__(self, method=None, url=None, headers=None, files=None,
data=None, params=None, auth=None, cookies=None, hooks=None, json=None):
# Default empty dicts for dict params.
data = [] if data is None else data
files = [] if files is None else files
headers = {} if headers is None else headers
params = {} if params is None else params
hooks = {} if hooks is None else hooks
self.hooks = default_hooks()
for (k, v) in list(hooks.items()):
self.register_hook(event=k, hook=v)
self.method = method
self.url = url
self.headers = headers
self.files = files
self.data = data
self.json = json
self.params = params
self.auth = auth
self.cookies = cookies
def __repr__(self):
return '<Request [%s]>' % (self.method)
def prepare(self):
"""Constructs a :class:`PreparedRequest <PreparedRequest>` for transmission and returns it."""
p = PreparedRequest()
p.prepare(
method=self.method,
url=self.url,
headers=self.headers,
files=self.files,
data=self.data,
json=self.json,
params=self.params,
auth=self.auth,
cookies=self.cookies,
hooks=self.hooks,
)
return p
models.py
request arguments
that were passed in
This is Requests
class definition](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-48-320.jpg)
![class PreparedRequest(RequestEncodingMixin, RequestHooksMixin):
"""The fully mutable :class:`PreparedRequest <PreparedRequest>` object,
containing the exact bytes that will be sent to the server.
Generated from either a :class:`Request <Request>` object or manually.
Usage::
>>> import requests
>>> req = requests.Request('GET', 'http://httpbin.org/get')
>>> r = req.prepare()
<PreparedRequest [GET]>
>>> s = requests.Session()
>>> s.send(r)
<Response [200]>
"""
def __init__(self):
#: HTTP verb to send to the server.
self.method = None
#: HTTP URL to send the request to.
self.url = None
#: dictionary of HTTP headers.
self.headers = None
# The `CookieJar` used to create the Cookie header will be stored here
# after prepare_cookies is called
self._cookies = None
#: request body to send to the server.
self.body = None
#: dictionary of callback hooks, for internal usage.
self.hooks = default_hooks()
def prepare(self, method=None, url=None, headers=None, files=None,
data=None, params=None, auth=None, cookies=None, hooks=None, json=None):
"""Prepares the entire request with the given parameters."""
self.prepare_method(method)
self.prepare_url(url, params)
self.prepare_headers(headers)
self.prepare_cookies(cookies)
self.prepare_body(data, files, json)
self.prepare_auth(auth, url)
# Note that prepare_auth must be last to enable authentication schemes
# such as OAuth to work on a fully prepared request.
# This MUST go after prepare_auth. Authenticators could add a hook
self.prepare_hooks(hooks)
models.py
W
hat are
Prepared
Requests?
Lots more
layers of
abstraction!](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-52-320.jpg)
![3. send request
4. return response
Let’s dissect requests/sessions.py
def send(self, request, **kwargs):
"""Send a given PreparedRequest."""
….[LONG METHOD DEFINITION HERE]….
return r
send()request object response object
sessions.py](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-54-320.jpg)
![def send(self, request, **kwargs):
"""Send a given PreparedRequest."""
# Set defaults that the hooks can utilize to ensure they
always have
# the correct parameters to reproduce the previous request.
kwargs.setdefault('stream', self.stream)
kwargs.setdefault('verify', self.verify)
kwargs.setdefault('cert', self.cert)
kwargs.setdefault('proxies', self.proxies)
# It's possible that users might accidentally send a Request
object.
# Guard against that specific failure case.
if not isinstance(request, PreparedRequest):
raise ValueError('You can only send PreparedRequests.')
checked_urls = set()
while request.url in self.redirect_cache:
checked_urls.add(request.url)
new_url = self.redirect_cache.get(request.url)
if new_url in checked_urls:
break
request.url = new_url
# Set up variables needed for resolve_redirects and
dispatching of hooks
allow_redirects = kwargs.pop('allow_redirects', True)
stream = kwargs.get('stream')
hooks = request.hooks
# Get the appropriate adapter to use
adapter = self.get_adapter(url=request.url)
# Start time (approximately) of the request
start = datetime.utcnow()
# Send the request
r = adapter.send(request, **kwargs)
# Total elapsed time of the request (approximately)
r.elapsed = datetime.utcnow() - start
# Response manipulation hooks
r = dispatch_hook('response', hooks, r, **kwargs)
# Persist cookies
if r.history:
# If the hooks create history then we want those cookies
too
for resp in r.history:
extract_cookies_to_jar(self.cookies, resp.request,
resp.raw)
extract_cookies_to_jar(self.cookies, request, r.raw)
# Redirect resolving generator.
gen = self.resolve_redirects(r, request, **kwargs)
# Resolve redirects if allowed.
history = [resp for resp in gen] if allow_redirects else []
# Shuffle things around if there's history.
if history:
# Insert the first (original) request at the start
history.insert(0, r)
# Get the last request made
r = history.pop()
r.history = history
if not stream:
r.content
return r
3. send request
4. return response
# Get the appropriate adapter to use
adapter = self.get_adapter(url=request.url)
# Start time (approximately) of the request
start = datetime.utcnow()
# Send the request
r = adapter.send(request, **kwargs)
sessions.py
What is the send method
doing in adapters.py?
What’s an adapter?](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-55-320.jpg)
![def send(self, request, stream=False, timeout=None, verify=True, cert=None, proxies=None):
"""Sends PreparedRequest object. Returns Response object.
:param request: The :class:`PreparedRequest <PreparedRequest>` being sent.
:param stream: (optional) Whether to stream the request content.
:param timeout: (optional) How long to wait for the server to send
data before giving up, as a float, or a :ref:`(connect timeout,
read timeout) <timeouts>` tuple.
:type timeout: float or tuple
:param verify: (optional) Whether to verify SSL certificates.
:param cert: (optional) Any user-provided SSL certificate to be trusted.
:param proxies: (optional) The proxies dictionary to apply to the request.
"""
conn = self.get_connection(request.url, proxies)
self.cert_verify(conn, request.url, verify, cert)
url = self.request_url(request, proxies)
self.add_headers(request)
chunked = not (request.body is None or 'Content-Length' in request.headers)
if isinstance(timeout, tuple):
try:
connect, read = timeout
timeout = TimeoutSauce(connect=connect, read=read)
except ValueError as e:
# this may raise a string formatting error.
err = ("Invalid timeout {0}. Pass a (connect, read) "
"timeout tuple, or a single float to set "
"both timeouts to the same value".format(timeout))
raise ValueError(err)
else:
timeout = TimeoutSauce(connect=timeout, read=timeout)
try:
if not chunked:
resp = conn.urlopen(
method=request.method,
url=url,
body=request.body,
headers=request.headers,
redirect=False,
assert_same_host=False,
preload_content=False,
decode_content=False,
retries=self.max_retries,
timeout=timeout
)
# Send the request.
else:
if hasattr(conn, 'proxy_pool'):
conn = conn.proxy_pool
low_conn = conn._get_conn(timeout=DEFAULT_POOL_TIMEOUT)
try:
low_conn.putrequest(request.method,
url,
skip_accept_encoding=True)
for header, value in request.headers.items():
low_conn.putheader(header, value)
low_conn.endheaders()
for i in request.body:
low_conn.send(hex(len(i))[2:].encode('utf-8'))
low_conn.send(b'rn')
low_conn.send(i)
low_conn.send(b'rn')
low_conn.send(b'0rnrn')
# Receive the response from the server
try:
# For Python 2.7+ versions, use buffering of HTTP
# responses
r = low_conn.getresponse(buffering=True)
except TypeError:
# For compatibility with Python 2.6 versions and back
r = low_conn.getresponse()
resp = HTTPResponse.from_httplib(
r,
pool=conn,
connection=low_conn,
preload_content=False,
decode_content=False
)
except:
# If we hit any problems here, clean up the connection.
# Then, reraise so that we can handle the actual exception.
low_conn.close()
raise
except (ProtocolError, socket.error) as err:
raise ConnectionError(err, request=request)
except MaxRetryError as e:
if isinstance(e.reason, ConnectTimeoutError):
# TODO: Remove this in 3.0.0: see #2811
if not isinstance(e.reason, NewConnectionError):
raise ConnectTimeout(e, request=request)
if isinstance(e.reason, ResponseError):
raise RetryError(e, request=request)
raise ConnectionError(e, request=request)
except ClosedPoolError as e:
raise ConnectionError(e, request=request)
except _ProxyError as e:
raise ProxyError(e)
except (_SSLError, _HTTPError) as e:
if isinstance(e, _SSLError):
raise SSLError(e, request=request)
elif isinstance(e, ReadTimeoutError):
raise ReadTimeout(e, request=request)
else:
raise
adapters.py
Size
5
font. This
is
the
definition
of send() m
ethod. Over
100
lines
long
and
it can’t fit this
slide.
Exercise
left to
reader to
read
thru
this
send() m
ethod.](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-58-320.jpg)
![Use pytest debugger to see output of send() method
[48] > /Users/susantan/Projects/requests/requests/
adapters.py(455)send()
-> return self.build_response(request, resp)
(Pdb++) request.url
‘http://127.0.0.1:58948/digest-auth/auth/user/pass'
(Pdb++) resp
<requests.packages.urllib3.response.HTTPResponse object
at 0x102c15110>
(Pdb++) our_version_of_response_object =
self.build_response(request, resp)
(Pdb++) our_version_of_response_object.json()
{u'authenticated': True, u'user': u’user'}
(Pdb++) our_version_of_response_object.status_code
200](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-61-320.jpg)
![Goal for today —
Figure out how this code snippet works
>>> r = requests.get('https://api.github.com/
user', auth=('user', 'pass'))
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"type":"User"...'
>>> r.json()
{u'private_gists': 419, u'total_private_repos':
77}](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-62-320.jpg)
![No walkthrough of a codebase is the same
for any person. ie: skip reading any unit test.
In [4]: import requests
In [4]: resp = requests.post('http://httpbin.org/post',
data={'name':'Susan'})
[14] > /Users/susantan/Projects/requests/requests/
adapters.py(346)send()
-> conn = self.get_connection(request.url, proxies)
(Pdb++) l
341 """
342
343 import pytest
344 pytest.set_trace()
345
346 -> conn = self.get_connection(request.url, proxies)
347
348 self.cert_verify(conn, request.url, verify, cert)
349 url = self.request_url(request, proxies)
350 self.add_headers(request)
351
(Pdb++) dir()
['cert', 'proxies', 'pytest', 'request', 'self', 'stream', 'timeout',
'verify']
Set breakpoints!](https://image.slidesharecdn.com/letsreadcode-160204055226/85/Let-s-read-code-the-python-requests-library-69-320.jpg)
![This is a talk about
1. how to actively read a new Python codebase
2. reading thru the python-requests codebase
“Indeed, the ratio of time spent reading versus
writing is well over 10 to 1. We are constantly
reading old code as part of the effort to write
new code. ...[Therefore,] making it easy to read
makes it easier to write.”
Robert C. Martin, Clean Code: A Handbook of Agile Software Craftsmanship](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-4-2048.jpg)
![Goal for today —
Figure out how this code snippet works
>>> r = requests.get('https://api.github.com/
user', auth=('user', 'pass'))
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"type":"User"...'
>>> r.json()
{u'private_gists': 419, u'total_private_repos':
77}](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-9-2048.jpg)
![httpbin’s /post/ endpoint is useful for testing requests
library
In [1]: import requests
In [2]: resp = requests.post('http://httpbin.org/post',
data={'name':'Susan'})
In [3]: resp.json()
Out[3]:
{u'args': {},
u'data': u'',
u'files': {},
u'form': {u'name': u'Susan'},
u'headers': {u'Accept': u'*/*',
u'Accept-Encoding': u'gzip, deflate',
u'Content-Length': u'10',
u'Content-Type': u'application/x-www-form-urlencoded',
u'Host': u'httpbin.org',
u'User-Agent': u'python-requests/2.9.1'},
u'json': None,
u'origin': u'50.148.141.36',
u'url': u'http://httpbin.org/post'}](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-27-2048.jpg)
![Goal for today —
Figure out how this code snippet works
>>> r = requests.get('https://api.github.com/
user', auth=('user', 'pass'))
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"type":"User"...'
>>> r.json()
{u'private_gists': 419, u'total_private_repos':
77}](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-35-2048.jpg)
![def request(method, url, **kwargs):
"""Constructs and sends a :class:`Request <Request>`.
:param method: method for the new :class:`Request` object.
:param url: URL for the new :class:`Request` object.
:param params: (optional) Dictionary or bytes to be sent in the query string for the :class:`Request`.
:param data: (optional) Dictionary, bytes, or file-like object to send in the body of the :class:`Request`.
:param json: (optional) json data to send in the body of the :class:`Request`.
:param headers: (optional) Dictionary of HTTP Headers to send with the :class:`Request`.
:param cookies: (optional) Dict or CookieJar object to send with the :class:`Request`.
:param files: (optional) Dictionary of ``'name': file-like-objects`` (or ``{'name': ('filename', fileobj)}``)
for multipart encoding upload.
:param auth: (optional) Auth tuple to enable Basic/Digest/Custom HTTP Auth.
:param timeout: (optional) How long to wait for the server to send data
before giving up, as a float, or a :ref:`(connect timeout, read
timeout) <timeouts>` tuple.
:type timeout: float or tuple
:param allow_redirects: (optional) Boolean. Set to True if POST/PUT/DELETE redirect following is allowed.
:type allow_redirects: bool
:param proxies: (optional) Dictionary mapping protocol to the URL of the proxy.
:param verify: (optional) whether the SSL cert will be verified. A CA_BUNDLE path can also be provided.
Defaults to ``True``.
:param stream: (optional) if ``False``, the response content will be immediately downloaded.
:param cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, ('cert', 'key') pair.
:return: :class:`Response <Response>` object
:rtype: requests.Response
Usage::
>>> import requests
>>> req = requests.request('GET', 'http://httpbin.org/get')
<Response [200]>
"""
# By using the 'with' statement we are sure the session is closed, thus we
# avoid leaving sockets open which can trigger a ResourceWarning in some
# cases, and look like a memory leak in others.
with sessions.Session() as session:
return session.request(method=method, url=url, **kwargs)
api.py
This is the request method](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-39-2048.jpg)
![class Session(SessionRedirectMixin):
"""A Requests session.
Provides cookie persistence, connection-pooling, and configuration.
Basic Usage::
>>> import requests
>>> s = requests.Session()
>>> s.get('http://httpbin.org/get')
<Response [200]>
Or as a context manager::
>>> with requests.Session() as s:
>>> s.get('http://httpbin.org/get')
<Response [200]>
"""
__attrs__ = [
'headers', 'cookies', 'auth', 'proxies', 'hooks', 'params', 'verify',
'cert', 'prefetch', 'adapters', 'stream', 'trust_env',
'max_redirects',
]
def __init__(self):
#: A case-insensitive dictionary of headers to be sent on each
#: :class:`Request <Request>` sent from this
#: :class:`Session <Session>`.
self.headers = default_headers()
#: Default Authentication tuple or object to attach to
#: :class:`Request <Request>`.
self.auth = None
#: Dictionary mapping protocol or protocol and host to the URL of the proxy
#: (e.g. {'http': 'foo.bar:3128', 'http://host.name': 'foo.bar:4012'}) to
#: be used on each :class:`Request <Request>`.
self.proxies = {}
#: Event-handling hooks.
self.hooks = default_hooks()
#: Dictionary of querystring data to attach to each
#: :class:`Request <Request>`. The dictionary values may be lists for
#: representing multivalued query parameters.
self.params = {}
#: Stream response content default.
self.stream = False
#: SSL Verification default.
self.verify = True
#: SSL certificate default.
self.cert = None
….
sessions.py
R
eally
long
class
definition
of“Sessions”](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-41-2048.jpg)
![class Request(RequestHooksMixin):
"""A user-created :class:`Request <Request>` object.
Used to prepare a :class:`PreparedRequest <PreparedRequest>`, which is sent to the server.
:param method: HTTP method to use.
:param url: URL to send.
:param headers: dictionary of headers to send.
:param files: dictionary of {filename: fileobject} files to multipart upload.
:param data: the body to attach to the request. If a dictionary is provided, form-encoding will take place.
:param json: json for the body to attach to the request (if files or data is not specified).
:param params: dictionary of URL parameters to append to the URL.
:param auth: Auth handler or (user, pass) tuple.
:param cookies: dictionary or CookieJar of cookies to attach to this request.
:param hooks: dictionary of callback hooks, for internal usage.
Usage::
>>> import requests
>>> req = requests.Request('GET', 'http://httpbin.org/get')
>>> req.prepare()
<PreparedRequest [GET]>
"""
def __init__(self, method=None, url=None, headers=None, files=None,
data=None, params=None, auth=None, cookies=None, hooks=None, json=None):
# Default empty dicts for dict params.
data = [] if data is None else data
files = [] if files is None else files
headers = {} if headers is None else headers
params = {} if params is None else params
hooks = {} if hooks is None else hooks
self.hooks = default_hooks()
for (k, v) in list(hooks.items()):
self.register_hook(event=k, hook=v)
self.method = method
self.url = url
self.headers = headers
self.files = files
self.data = data
self.json = json
self.params = params
self.auth = auth
self.cookies = cookies
def __repr__(self):
return '<Request [%s]>' % (self.method)
def prepare(self):
"""Constructs a :class:`PreparedRequest <PreparedRequest>` for transmission and returns it."""
p = PreparedRequest()
p.prepare(
method=self.method,
url=self.url,
headers=self.headers,
files=self.files,
data=self.data,
json=self.json,
params=self.params,
auth=self.auth,
cookies=self.cookies,
hooks=self.hooks,
)
return p
models.py
request arguments
that were passed in
This is Requests
class definition](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-48-2048.jpg)
![class PreparedRequest(RequestEncodingMixin, RequestHooksMixin):
"""The fully mutable :class:`PreparedRequest <PreparedRequest>` object,
containing the exact bytes that will be sent to the server.
Generated from either a :class:`Request <Request>` object or manually.
Usage::
>>> import requests
>>> req = requests.Request('GET', 'http://httpbin.org/get')
>>> r = req.prepare()
<PreparedRequest [GET]>
>>> s = requests.Session()
>>> s.send(r)
<Response [200]>
"""
def __init__(self):
#: HTTP verb to send to the server.
self.method = None
#: HTTP URL to send the request to.
self.url = None
#: dictionary of HTTP headers.
self.headers = None
# The `CookieJar` used to create the Cookie header will be stored here
# after prepare_cookies is called
self._cookies = None
#: request body to send to the server.
self.body = None
#: dictionary of callback hooks, for internal usage.
self.hooks = default_hooks()
def prepare(self, method=None, url=None, headers=None, files=None,
data=None, params=None, auth=None, cookies=None, hooks=None, json=None):
"""Prepares the entire request with the given parameters."""
self.prepare_method(method)
self.prepare_url(url, params)
self.prepare_headers(headers)
self.prepare_cookies(cookies)
self.prepare_body(data, files, json)
self.prepare_auth(auth, url)
# Note that prepare_auth must be last to enable authentication schemes
# such as OAuth to work on a fully prepared request.
# This MUST go after prepare_auth. Authenticators could add a hook
self.prepare_hooks(hooks)
models.py
W
hat are
Prepared
Requests?
Lots more
layers of
abstraction!](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-52-2048.jpg)
![3. send request
4. return response
Let’s dissect requests/sessions.py
def send(self, request, **kwargs):
"""Send a given PreparedRequest."""
….[LONG METHOD DEFINITION HERE]….
return r
send()request object response object
sessions.py](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-54-2048.jpg)
![def send(self, request, **kwargs):
"""Send a given PreparedRequest."""
# Set defaults that the hooks can utilize to ensure they
always have
# the correct parameters to reproduce the previous request.
kwargs.setdefault('stream', self.stream)
kwargs.setdefault('verify', self.verify)
kwargs.setdefault('cert', self.cert)
kwargs.setdefault('proxies', self.proxies)
# It's possible that users might accidentally send a Request
object.
# Guard against that specific failure case.
if not isinstance(request, PreparedRequest):
raise ValueError('You can only send PreparedRequests.')
checked_urls = set()
while request.url in self.redirect_cache:
checked_urls.add(request.url)
new_url = self.redirect_cache.get(request.url)
if new_url in checked_urls:
break
request.url = new_url
# Set up variables needed for resolve_redirects and
dispatching of hooks
allow_redirects = kwargs.pop('allow_redirects', True)
stream = kwargs.get('stream')
hooks = request.hooks
# Get the appropriate adapter to use
adapter = self.get_adapter(url=request.url)
# Start time (approximately) of the request
start = datetime.utcnow()
# Send the request
r = adapter.send(request, **kwargs)
# Total elapsed time of the request (approximately)
r.elapsed = datetime.utcnow() - start
# Response manipulation hooks
r = dispatch_hook('response', hooks, r, **kwargs)
# Persist cookies
if r.history:
# If the hooks create history then we want those cookies
too
for resp in r.history:
extract_cookies_to_jar(self.cookies, resp.request,
resp.raw)
extract_cookies_to_jar(self.cookies, request, r.raw)
# Redirect resolving generator.
gen = self.resolve_redirects(r, request, **kwargs)
# Resolve redirects if allowed.
history = [resp for resp in gen] if allow_redirects else []
# Shuffle things around if there's history.
if history:
# Insert the first (original) request at the start
history.insert(0, r)
# Get the last request made
r = history.pop()
r.history = history
if not stream:
r.content
return r
3. send request
4. return response
# Get the appropriate adapter to use
adapter = self.get_adapter(url=request.url)
# Start time (approximately) of the request
start = datetime.utcnow()
# Send the request
r = adapter.send(request, **kwargs)
sessions.py
What is the send method
doing in adapters.py?
What’s an adapter?](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-55-2048.jpg)
![def send(self, request, stream=False, timeout=None, verify=True, cert=None, proxies=None):
"""Sends PreparedRequest object. Returns Response object.
:param request: The :class:`PreparedRequest <PreparedRequest>` being sent.
:param stream: (optional) Whether to stream the request content.
:param timeout: (optional) How long to wait for the server to send
data before giving up, as a float, or a :ref:`(connect timeout,
read timeout) <timeouts>` tuple.
:type timeout: float or tuple
:param verify: (optional) Whether to verify SSL certificates.
:param cert: (optional) Any user-provided SSL certificate to be trusted.
:param proxies: (optional) The proxies dictionary to apply to the request.
"""
conn = self.get_connection(request.url, proxies)
self.cert_verify(conn, request.url, verify, cert)
url = self.request_url(request, proxies)
self.add_headers(request)
chunked = not (request.body is None or 'Content-Length' in request.headers)
if isinstance(timeout, tuple):
try:
connect, read = timeout
timeout = TimeoutSauce(connect=connect, read=read)
except ValueError as e:
# this may raise a string formatting error.
err = ("Invalid timeout {0}. Pass a (connect, read) "
"timeout tuple, or a single float to set "
"both timeouts to the same value".format(timeout))
raise ValueError(err)
else:
timeout = TimeoutSauce(connect=timeout, read=timeout)
try:
if not chunked:
resp = conn.urlopen(
method=request.method,
url=url,
body=request.body,
headers=request.headers,
redirect=False,
assert_same_host=False,
preload_content=False,
decode_content=False,
retries=self.max_retries,
timeout=timeout
)
# Send the request.
else:
if hasattr(conn, 'proxy_pool'):
conn = conn.proxy_pool
low_conn = conn._get_conn(timeout=DEFAULT_POOL_TIMEOUT)
try:
low_conn.putrequest(request.method,
url,
skip_accept_encoding=True)
for header, value in request.headers.items():
low_conn.putheader(header, value)
low_conn.endheaders()
for i in request.body:
low_conn.send(hex(len(i))[2:].encode('utf-8'))
low_conn.send(b'rn')
low_conn.send(i)
low_conn.send(b'rn')
low_conn.send(b'0rnrn')
# Receive the response from the server
try:
# For Python 2.7+ versions, use buffering of HTTP
# responses
r = low_conn.getresponse(buffering=True)
except TypeError:
# For compatibility with Python 2.6 versions and back
r = low_conn.getresponse()
resp = HTTPResponse.from_httplib(
r,
pool=conn,
connection=low_conn,
preload_content=False,
decode_content=False
)
except:
# If we hit any problems here, clean up the connection.
# Then, reraise so that we can handle the actual exception.
low_conn.close()
raise
except (ProtocolError, socket.error) as err:
raise ConnectionError(err, request=request)
except MaxRetryError as e:
if isinstance(e.reason, ConnectTimeoutError):
# TODO: Remove this in 3.0.0: see #2811
if not isinstance(e.reason, NewConnectionError):
raise ConnectTimeout(e, request=request)
if isinstance(e.reason, ResponseError):
raise RetryError(e, request=request)
raise ConnectionError(e, request=request)
except ClosedPoolError as e:
raise ConnectionError(e, request=request)
except _ProxyError as e:
raise ProxyError(e)
except (_SSLError, _HTTPError) as e:
if isinstance(e, _SSLError):
raise SSLError(e, request=request)
elif isinstance(e, ReadTimeoutError):
raise ReadTimeout(e, request=request)
else:
raise
adapters.py
Size
5
font. This
is
the
definition
of send() m
ethod. Over
100
lines
long
and
it can’t fit this
slide.
Exercise
left to
reader to
read
thru
this
send() m
ethod.](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-58-2048.jpg)
![Use pytest debugger to see output of send() method
[48] > /Users/susantan/Projects/requests/requests/
adapters.py(455)send()
-> return self.build_response(request, resp)
(Pdb++) request.url
‘http://127.0.0.1:58948/digest-auth/auth/user/pass'
(Pdb++) resp
<requests.packages.urllib3.response.HTTPResponse object
at 0x102c15110>
(Pdb++) our_version_of_response_object =
self.build_response(request, resp)
(Pdb++) our_version_of_response_object.json()
{u'authenticated': True, u'user': u’user'}
(Pdb++) our_version_of_response_object.status_code
200](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-61-2048.jpg)
![Goal for today —
Figure out how this code snippet works
>>> r = requests.get('https://api.github.com/
user', auth=('user', 'pass'))
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"type":"User"...'
>>> r.json()
{u'private_gists': 419, u'total_private_repos':
77}](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-62-2048.jpg)
![No walkthrough of a codebase is the same
for any person. ie: skip reading any unit test.
In [4]: import requests
In [4]: resp = requests.post('http://httpbin.org/post',
data={'name':'Susan'})
[14] > /Users/susantan/Projects/requests/requests/
adapters.py(346)send()
-> conn = self.get_connection(request.url, proxies)
(Pdb++) l
341 """
342
343 import pytest
344 pytest.set_trace()
345
346 -> conn = self.get_connection(request.url, proxies)
347
348 self.cert_verify(conn, request.url, verify, cert)
349 url = self.request_url(request, proxies)
350 self.add_headers(request)
351
(Pdb++) dir()
['cert', 'proxies', 'pytest', 'request', 'self', 'stream', 'timeout',
'verify']
Set breakpoints!](https://image.slidesharecdn.com/letsreadcode-160204055226/75/Let-s-read-code-the-python-requests-library-69-2048.jpg)
Uploaded bySusan Tan
Let's read code: the python-requests library
- The document discusses reading through the python-requests codebase by cloning the requests repository, setting up a local development environment, and examining unit tests and code snippets. - It demonstrates using the requests.get method in a unit test, looking at the HTTPDigestAuth class definition, and using the httpbin fixture and httpbin.org site to test authentication. - Key points are that httpbin is used extensively in unit tests to make requests, sessions persist request parameters and use connection pooling, and the requests documentation provides helpful references.
More Related Content
Similar to Let's read code: the python-requests library
Let's read code: the python-requests library
- 1. $ git clonehttps://github.com/ kennethreitz/requests $ cd requests $ subl requests (or editor of choice) Optionally, feel free to follow along with your local copy of the requests repo. Slides: http://www.slideshare.net/onceuponatimeforever/ lets-read-code Let’s read code
- 2. Let’s read code: python-requestslibrary Susan Tan Twitter: @ArcTanSusan PyTN 2016 February 7, 2016 Nashville, TN 2
- 3. First time yougit clone and open a new repo
- 4. This is atalk about 1. how to actively read a new Python codebase 2. reading thru the python-requests codebase “Indeed, the ratio of time spent reading versus writing is well over 10 to 1. We are constantly reading old code as part of the effort to write new code. ...[Therefore,] making it easy to read makes it easier to write.” Robert C. Martin, Clean Code: A Handbook of Agile Software Craftsmanship
- 5. Set up youreditor to • jump into any method or class definition • search files by keywords • get call hierarchy of any given method or class Note: I’ll be using Sublime Text with python-requests library. Step 0: Prepare Your Editor
- 6. Step 1: Gitclone and open the repo $ git clone https://github.com/ kennethreitz/requests $ cd requests $ subl requests
- 7. Step 2: Setup local dev environment to get into mindset of a contributor python test_requests.py works too. Source: http://docs.python-requests.org/en/latest/dev/todo/#development-dependencies
- 8. What it’s liketo read a large codebase Once you’ve set up your editor & local dev environment…
- 9. Goal for today— Figure out how this code snippet works >>> r = requests.get('https://api.github.com/ user', auth=('user', 'pass')) >>> r.status_code 200 >>> r.headers['content-type'] 'application/json; charset=utf8' >>> r.encoding 'utf-8' >>> r.text u'{"type":"User"...' >>> r.json() {u'private_gists': 419, u'total_private_repos': 77}
- 10. Step 3: Lookat unit tests • Over 1,700 lines of code in test_requests.py. Where to look first? • Use git grep or keyword search for “requests.get”
- 11. git grep requests.gettest_requests.py $ git grep requests.get test_requests.py test_requests.py:95: requests.get test_requests.py:103: requests.get('hiwpefhipowhefopw') test_requests.py:105: requests.get('localhost:3128') test_requests.py:107: requests.get('localhost.localdomain:3128/') test_requests.py:109: requests.get('10.122.1.1:3128/') test_requests.py:111: requests.get('http://') test_requests.py:187: r = requests.get(httpbin('redirect', '1')) test_requests.py:199: r = requests.get(httpbin('user-agent'), headers=heads) test_requests.py:207: r = requests.get(httpbin('get') + '? test=true', params={'q': 'test'}, headers=heads) test_requests.py:280: resp = requests.get(httpbin('redirect/ 3')) test_requests.py:289: resp = requests.get(httpbin('get')) test_requests.py:291: resp = requests.get(httpbin('redirect/ 1')) ...... $ git grep requests.get test_requests.py | wc -l 56
- 12. Let’s look atone unit test
- 13. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') r = requests.get(url, auth=auth) assert r.status_code == 200 r = requests.get(url) assert r.status_code == 401 s = requests.session() s.auth = HTTPDigestAuth('user', 'pass') r = s.get(url) assert r.status_code == 200 test_requests.py Looks like test setup happens here
- 14. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') r = requests.get(url, auth=auth) assert r.status_code == 200 r = requests.get(url) assert r.status_code == 401 s = requests.session() s.auth = HTTPDigestAuth('user', 'pass') r = s.get(url) assert r.status_code == 200 test_requests.py MUST be a string type 401 means forbidden. This is a test to confirm auth object is required.
- 15. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') r = requests.get(url, auth=auth) assert r.status_code == 200 r = requests.get(url) assert r.status_code == 401 s = requests.session() s.auth = HTTPDigestAuth('user', 'pass') r = s.get(url) assert r.status_code == 200 test_requests.pyWhat’s a session?
- 16. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') r = requests.get(url, auth=auth) assert r.status_code == 200 r = requests.get(url) assert r.status_code == 401 s = requests.session() s.auth = HTTPDigestAuth('user', 'pass') r = s.get(url) assert r.status_code == 200 test_requests.py Let’s look at class definition
- 17. class HTTPDigestAuth(AuthBase): """Attaches HTTPDigest Authentication to the given Request object.""" def __init__(self, username, password): self.username = username self.password = password # Keep state in per-thread local storage self._thread_local = threading.local() def init_per_thread_state(self): # Ensure state is initialized just once per-thread … def build_digest_header(self, method, url): … def handle_redirect(self, r, **kwargs): … def handle_401(self, r, **kwargs): … def __call__(self, r): … What is the HTTPDigestAuth class? auth.py
- 18.
- 19. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') r = requests.get(url, auth=auth) assert r.status_code == 200 r = requests.get(url) assert r.status_code == 401 s = requests.session() s.auth = HTTPDigestAuth('user', 'pass') r = s.get(url) assert r.status_code == 200 test_requests.py Let’s look at method definition
- 20. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') test_requests.py Let’s look at method definition @pytest.fixture def httpbin(httpbin): httpbin_url = httpbin.url.rstrip('/') + '/' def inner(*suffix): return urljoin(httpbin_url, '/'.join(suffix)) return inner This is httpbin() method:
- 22. I’m still confusedby what httpbin() method is doing. Next steps: • look up “httpbin” in official request docs. • If that fails, then use a debugger. We’ll do both.
- 23. I type in“httpbin”
- 24.
- 25. https://github.com/Runscope/ httpbin Next Step: Let’stry out this http:// httpbin.org/.
- 26. http://httpbin.org/cookies http://httpbin.org/get Next Step: Let’stry out this http://httpbin.org/
- 27. httpbin’s /post/ endpointis useful for testing requests library In [1]: import requests In [2]: resp = requests.post('http://httpbin.org/post', data={'name':'Susan'}) In [3]: resp.json() Out[3]: {u'args': {}, u'data': u'', u'files': {}, u'form': {u'name': u'Susan'}, u'headers': {u'Accept': u'*/*', u'Accept-Encoding': u'gzip, deflate', u'Content-Length': u'10', u'Content-Type': u'application/x-www-form-urlencoded', u'Host': u'httpbin.org', u'User-Agent': u'python-requests/2.9.1'}, u'json': None, u'origin': u'50.148.141.36', u'url': u'http://httpbin.org/post'}
- 28. • httpbin iseverywhere in unit tests in the requests repo every time a request is made. • This is a BIG step forward in our understanding of unit tests in this repo. httpbin endpoints and requests unit test
- 29. pytest.set_trace() Side Note: Youcan use pytest debugger I placed a debugger in the httpbin method to see what the output “url” looks like.
- 30. @pytest.fixture def httpbin(httpbin): # Issue#1483: Make sure the URL always has a trailing slash httpbin_url = httpbin.url.rstrip('/') + '/' pytest.set_trace() def inner(*suffix): return urljoin(httpbin_url, '/'.join(suffix)) pytest.set_trace() return inner def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth = HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', 'auth', 'user', 'pass') r = requests.get(url, auth=auth) pytest.set_trace() assert r.status_code == 200 test_requests.py
- 31. py.test test_requests.py::TestRequests::test_DIGEST_HTTP_200_OK_GET Side Note:You can use pytest debugger
- 32. Side Note: Youcan use pytest debugger
- 33. What is thisurl http://127.0.0.01:73720/ digest-auth/auth/user/pass?! Side Note: You can use pytest debugger
- 34. What is httpbin.org/digest-auth/auth/user/pass? Unittest gives me the answers to both fields. I type in “user” and “pass” in both fields. The result? ✓
- 35. Goal for today— Figure out how this code snippet works >>> r = requests.get('https://api.github.com/ user', auth=('user', 'pass')) >>> r.status_code 200 >>> r.headers['content-type'] 'application/json; charset=utf8' >>> r.encoding 'utf-8' >>> r.text u'{"type":"User"...' >>> r.json() {u'private_gists': 419, u'total_private_repos': 77}
- 36. Let’s look atone unit test
- 37. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') r = requests.get(url, auth=auth) assert r.status_code == 200 r = requests.get(url) assert r.status_code == 401 s = requests.session() s.auth = HTTPDigestAuth('user', 'pass') r = s.get(url) assert r.status_code == 200 test_requests.py Let’s look at definition of request method
- 38. def get(url, params=None,**kwargs): """Sends a GET request. :param url: URL for the new :class:`Request` object. :param params: (optional) Dictionary or bytes to be sent in the query string for the :class:`Request`. :param **kwargs: Optional arguments that ``request`` takes. :return: :class:`Response <Response>` object :rtype: requests.Response """ kwargs.setdefault('allow_redirects', True) return request('get', url, params=params, **kwargs) This is the get method What’s happening here? • Set default dict of key-value pairs to allow redirects by default • Returns a request. What’s a request? Look at method above. api.py
- 39. def request(method, url,**kwargs): """Constructs and sends a :class:`Request <Request>`. :param method: method for the new :class:`Request` object. :param url: URL for the new :class:`Request` object. :param params: (optional) Dictionary or bytes to be sent in the query string for the :class:`Request`. :param data: (optional) Dictionary, bytes, or file-like object to send in the body of the :class:`Request`. :param json: (optional) json data to send in the body of the :class:`Request`. :param headers: (optional) Dictionary of HTTP Headers to send with the :class:`Request`. :param cookies: (optional) Dict or CookieJar object to send with the :class:`Request`. :param files: (optional) Dictionary of ``'name': file-like-objects`` (or ``{'name': ('filename', fileobj)}``) for multipart encoding upload. :param auth: (optional) Auth tuple to enable Basic/Digest/Custom HTTP Auth. :param timeout: (optional) How long to wait for the server to send data before giving up, as a float, or a :ref:`(connect timeout, read timeout) <timeouts>` tuple. :type timeout: float or tuple :param allow_redirects: (optional) Boolean. Set to True if POST/PUT/DELETE redirect following is allowed. :type allow_redirects: bool :param proxies: (optional) Dictionary mapping protocol to the URL of the proxy. :param verify: (optional) whether the SSL cert will be verified. A CA_BUNDLE path can also be provided. Defaults to ``True``. :param stream: (optional) if ``False``, the response content will be immediately downloaded. :param cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, ('cert', 'key') pair. :return: :class:`Response <Response>` object :rtype: requests.Response Usage:: >>> import requests >>> req = requests.request('GET', 'http://httpbin.org/get') <Response [200]> """ # By using the 'with' statement we are sure the session is closed, thus we # avoid leaving sockets open which can trigger a ResourceWarning in some # cases, and look like a memory leak in others. with sessions.Session() as session: return session.request(method=method, url=url, **kwargs) api.py This is the request method
- 40. def request(method, url,**kwargs): with sessions.Session() as session: return session.request(method=method, url=url, **kwargs) What are sessions?? api.py This is the same request method without docstrings or comments
- 41. class Session(SessionRedirectMixin): """A Requestssession. Provides cookie persistence, connection-pooling, and configuration. Basic Usage:: >>> import requests >>> s = requests.Session() >>> s.get('http://httpbin.org/get') <Response [200]> Or as a context manager:: >>> with requests.Session() as s: >>> s.get('http://httpbin.org/get') <Response [200]> """ __attrs__ = [ 'headers', 'cookies', 'auth', 'proxies', 'hooks', 'params', 'verify', 'cert', 'prefetch', 'adapters', 'stream', 'trust_env', 'max_redirects', ] def __init__(self): #: A case-insensitive dictionary of headers to be sent on each #: :class:`Request <Request>` sent from this #: :class:`Session <Session>`. self.headers = default_headers() #: Default Authentication tuple or object to attach to #: :class:`Request <Request>`. self.auth = None #: Dictionary mapping protocol or protocol and host to the URL of the proxy #: (e.g. {'http': 'foo.bar:3128', 'http://host.name': 'foo.bar:4012'}) to #: be used on each :class:`Request <Request>`. self.proxies = {} #: Event-handling hooks. self.hooks = default_hooks() #: Dictionary of querystring data to attach to each #: :class:`Request <Request>`. The dictionary values may be lists for #: representing multivalued query parameters. self.params = {} #: Stream response content default. self.stream = False #: SSL Verification default. self.verify = True #: SSL certificate default. self.cert = None …. sessions.py R eally long class definition of“Sessions”
- 42.
- 43. What’s a session? •an object that persists parameters across requests • makes use of urllib3’s connection pooling • has all methods of request API • provides default data to request object • note: requests has well written docs
- 44. def request(method, url,**kwargs): with sessions.Session() as session: return session.request(method=method, url=url, **kwargs) What is this request() in sessions? api.py This is the same request method without docstrings or comments
- 45. sessions.py def request(self, method,url, params=None, data=None, headers=None, cookies=None, files=None, auth=None, timeout=None, allow_redirects=True, proxies=None, hooks=None, stream=None, verify=None, cert=None, json=None): # Create the Request. req = Request( method = method.upper(), url = url, headers = headers, files = files, data = data or {}, json = json, params = params or {}, auth = auth, cookies = cookies, hooks = hooks, ) prep = self.prepare_request(req) proxies = proxies or {} settings = self.merge_environment_settings( prep.url, proxies, stream, verify, cert ) # Send the request. send_kwargs = { 'timeout': timeout, 'allow_redirects': allow_redirects, } send_kwargs.update(settings) resp = self.send(prep, **send_kwargs) return resp What is this request() in sessions?
- 46. # Create theRequest. req = Request( method = method.upper(), url = url, headers = headers, files = files, data = data or {}, json = json, params = params or {}, auth = auth, cookies = cookies, hooks = hooks, ) def request(self, method, url, params=None, data=None, headers=None, cookies=None, files=None, auth=None, timeout=None, allow_redirects=True, proxies=None, hooks=None, stream=None, verify=None, cert=None, json=None): # Create the Request. req = Request( method = method.upper(), url = url, headers = headers, files = files, data = data or {}, json = json, params = params or {}, auth = auth, cookies = cookies, hooks = hooks, ) prep = self.prepare_request(req) proxies = proxies or {} settings = self.merge_environment_settings( prep.url, proxies, stream, verify, cert ) # Send the request. send_kwargs = { 'timeout': timeout, 'allow_redirects': allow_redirects, } send_kwargs.update(settings) resp = self.send(prep, **send_kwargs) return resp sessions.py What’s happening in this code? 1. create request 2. create prepare request object “prep” 3. send request 4. return response 1 2 3 4
- 47. 1.create request Let’s dissectrequests/sessions.py
- 48. class Request(RequestHooksMixin): """A user-created:class:`Request <Request>` object. Used to prepare a :class:`PreparedRequest <PreparedRequest>`, which is sent to the server. :param method: HTTP method to use. :param url: URL to send. :param headers: dictionary of headers to send. :param files: dictionary of {filename: fileobject} files to multipart upload. :param data: the body to attach to the request. If a dictionary is provided, form-encoding will take place. :param json: json for the body to attach to the request (if files or data is not specified). :param params: dictionary of URL parameters to append to the URL. :param auth: Auth handler or (user, pass) tuple. :param cookies: dictionary or CookieJar of cookies to attach to this request. :param hooks: dictionary of callback hooks, for internal usage. Usage:: >>> import requests >>> req = requests.Request('GET', 'http://httpbin.org/get') >>> req.prepare() <PreparedRequest [GET]> """ def __init__(self, method=None, url=None, headers=None, files=None, data=None, params=None, auth=None, cookies=None, hooks=None, json=None): # Default empty dicts for dict params. data = [] if data is None else data files = [] if files is None else files headers = {} if headers is None else headers params = {} if params is None else params hooks = {} if hooks is None else hooks self.hooks = default_hooks() for (k, v) in list(hooks.items()): self.register_hook(event=k, hook=v) self.method = method self.url = url self.headers = headers self.files = files self.data = data self.json = json self.params = params self.auth = auth self.cookies = cookies def __repr__(self): return '<Request [%s]>' % (self.method) def prepare(self): """Constructs a :class:`PreparedRequest <PreparedRequest>` for transmission and returns it.""" p = PreparedRequest() p.prepare( method=self.method, url=self.url, headers=self.headers, files=self.files, data=self.data, json=self.json, params=self.params, auth=self.auth, cookies=self.cookies, hooks=self.hooks, ) return p models.py request arguments that were passed in This is Requests class definition
- 49. def request(self, method,url, params=None, data=None, headers=None, cookies=None, files=None, auth=None, timeout=None, allow_redirects=True, proxies=None, hooks=None, stream=None, verify=None, cert=None, json=None): # Create the Request. req = Request( method = method.upper(), url = url, headers = headers, files = files, data = data or {}, json = json, params = params or {}, auth = auth, cookies = cookies, hooks = hooks, ) prep = self.prepare_request(req) proxies = proxies or {} settings = self.merge_environment_settings( prep.url, proxies, stream, verify, cert ) # Send the request. send_kwargs = { 'timeout': timeout, 'allow_redirects': allow_redirects, } send_kwargs.update(settings) resp = self.send(prep, **send_kwargs) return resp sessions.py What’s happening in this code? 1. create request 2. create prepare request object “prep” 3. send request 4. return response1 2 3 4 ✓ prep = self.prepare_request( req)
- 50. 2. create preparerequest object “prep” Let’s dissect requests/sessions.py
- 51. def prepare_request(self, request): """Constructsa :class:`PreparedRequest <PreparedRequest>` for transmission and returns it. The :class:`PreparedRequest` has settings merged from the :class:`Request <Request>` instance and those of the :class:`Session`. :param request: :class:`Request` instance to prepare with this session's settings. """ cookies = request.cookies or {} # Bootstrap CookieJar. if not isinstance(cookies, cookielib.CookieJar): cookies = cookiejar_from_dict(cookies) # Merge with session cookies merged_cookies = merge_cookies( merge_cookies(RequestsCookieJar(), self.cookies), cookies) # Set environment's basic authentication if not explicitly set. auth = request.auth if self.trust_env and not auth and not self.auth: auth = get_netrc_auth(request.url) p = PreparedRequest() p.prepare( method=request.method.upper(), url=request.url, files=request.files, data=request.data, json=request.json, headers=merge_setting(request.headers, self.headers, dict_class=CaseInsensitiveDict), params=merge_setting(request.params, self.params), auth=merge_setting(auth, self.auth), cookies=merged_cookies, hooks=merge_hooks(request.hooks, self.hooks), ) return p What is “prepare_ request()”? sessions.py setup stuff happens “PreparedRequests class”? What is the class method “prepare()”?
- 52. class PreparedRequest(RequestEncodingMixin, RequestHooksMixin): """Thefully mutable :class:`PreparedRequest <PreparedRequest>` object, containing the exact bytes that will be sent to the server. Generated from either a :class:`Request <Request>` object or manually. Usage:: >>> import requests >>> req = requests.Request('GET', 'http://httpbin.org/get') >>> r = req.prepare() <PreparedRequest [GET]> >>> s = requests.Session() >>> s.send(r) <Response [200]> """ def __init__(self): #: HTTP verb to send to the server. self.method = None #: HTTP URL to send the request to. self.url = None #: dictionary of HTTP headers. self.headers = None # The `CookieJar` used to create the Cookie header will be stored here # after prepare_cookies is called self._cookies = None #: request body to send to the server. self.body = None #: dictionary of callback hooks, for internal usage. self.hooks = default_hooks() def prepare(self, method=None, url=None, headers=None, files=None, data=None, params=None, auth=None, cookies=None, hooks=None, json=None): """Prepares the entire request with the given parameters.""" self.prepare_method(method) self.prepare_url(url, params) self.prepare_headers(headers) self.prepare_cookies(cookies) self.prepare_body(data, files, json) self.prepare_auth(auth, url) # Note that prepare_auth must be last to enable authentication schemes # such as OAuth to work on a fully prepared request. # This MUST go after prepare_auth. Authenticators could add a hook self.prepare_hooks(hooks) models.py W hat are Prepared Requests? Lots more layers of abstraction!
- 53. def request(self, method,url, params=None, data=None, headers=None, cookies=None, files=None, auth=None, timeout=None, allow_redirects=True, proxies=None, hooks=None, stream=None, verify=None, cert=None, json=None): # Create the Request. req = Request( method = method.upper(), url = url, headers = headers, files = files, data = data or {}, json = json, params = params or {}, auth = auth, cookies = cookies, hooks = hooks, ) prep = self.prepare_request(req) proxies = proxies or {} settings = self.merge_environment_settings( prep.url, proxies, stream, verify, cert ) # Send the request. send_kwargs = { 'timeout': timeout, 'allow_redirects': allow_redirects, } send_kwargs.update(settings) resp = self.send(prep, **send_kwargs) return resp sessions.py What’s happening in this code? 1. create request 2. create prepare request object “prep” 3. send request 4. return response1 2 3 4 ✓ ✓ resp = self.send(prep, **send_kwargs) return resp
- 54. 3. send request 4.return response Let’s dissect requests/sessions.py def send(self, request, **kwargs): """Send a given PreparedRequest.""" ….[LONG METHOD DEFINITION HERE]…. return r send()request object response object sessions.py
- 55. def send(self, request,**kwargs): """Send a given PreparedRequest.""" # Set defaults that the hooks can utilize to ensure they always have # the correct parameters to reproduce the previous request. kwargs.setdefault('stream', self.stream) kwargs.setdefault('verify', self.verify) kwargs.setdefault('cert', self.cert) kwargs.setdefault('proxies', self.proxies) # It's possible that users might accidentally send a Request object. # Guard against that specific failure case. if not isinstance(request, PreparedRequest): raise ValueError('You can only send PreparedRequests.') checked_urls = set() while request.url in self.redirect_cache: checked_urls.add(request.url) new_url = self.redirect_cache.get(request.url) if new_url in checked_urls: break request.url = new_url # Set up variables needed for resolve_redirects and dispatching of hooks allow_redirects = kwargs.pop('allow_redirects', True) stream = kwargs.get('stream') hooks = request.hooks # Get the appropriate adapter to use adapter = self.get_adapter(url=request.url) # Start time (approximately) of the request start = datetime.utcnow() # Send the request r = adapter.send(request, **kwargs) # Total elapsed time of the request (approximately) r.elapsed = datetime.utcnow() - start # Response manipulation hooks r = dispatch_hook('response', hooks, r, **kwargs) # Persist cookies if r.history: # If the hooks create history then we want those cookies too for resp in r.history: extract_cookies_to_jar(self.cookies, resp.request, resp.raw) extract_cookies_to_jar(self.cookies, request, r.raw) # Redirect resolving generator. gen = self.resolve_redirects(r, request, **kwargs) # Resolve redirects if allowed. history = [resp for resp in gen] if allow_redirects else [] # Shuffle things around if there's history. if history: # Insert the first (original) request at the start history.insert(0, r) # Get the last request made r = history.pop() r.history = history if not stream: r.content return r 3. send request 4. return response # Get the appropriate adapter to use adapter = self.get_adapter(url=request.url) # Start time (approximately) of the request start = datetime.utcnow() # Send the request r = adapter.send(request, **kwargs) sessions.py What is the send method doing in adapters.py? What’s an adapter?
- 56. What’s an adapter? “TransportAdapters provide a mechanism to define interaction methods for an HTTP service. Requests ships with a single Transport Adapter, the HTTPAdapter. This adapter provides the default Requests interaction with HTTP and HTTPS using the powerful urllib3 library. Whenever a Requests session is initialized, one of these is attached to the session object for HTTP, and one for HTTPS.” —“Transport Adapters” in requests advanced docs
- 57. class HTTPAdapter(BaseAdapter): """ The built-inHTTP Adapter for urllib3. Provides a general-case interface for Requests sessions to contact HTTP and HTTPS urls by implementing the Transport Adapter interface. This class will usually be created by the :class:`Session <Session>` class under the covers. :param pool_connections: The number of urllib3 connection pools to cache. :param pool_maxsize: The maximum number of connections to save in the pool. :param int max_retries: The maximum number of retries each connection should attempt. Note, this applies only to failed DNS lookups, socket connections and connection timeouts, never to requests where data has made it to the server. By default, Requests does not retry failed connections. If you need granular control over the conditions under which we retry a request, import urllib3's ``Retry`` class and pass that instead. :param pool_block: Whether the connection pool should block for connections. Usage:: >>> import requests >>> s = requests.Session() >>> a = requests.adapters.HTTPAdapter(max_retries=3) >>> s.mount('http://', a) """ This is HTTPAdapter class, the interface for urllib3 adapters.py
- 58. def send(self, request,stream=False, timeout=None, verify=True, cert=None, proxies=None): """Sends PreparedRequest object. Returns Response object. :param request: The :class:`PreparedRequest <PreparedRequest>` being sent. :param stream: (optional) Whether to stream the request content. :param timeout: (optional) How long to wait for the server to send data before giving up, as a float, or a :ref:`(connect timeout, read timeout) <timeouts>` tuple. :type timeout: float or tuple :param verify: (optional) Whether to verify SSL certificates. :param cert: (optional) Any user-provided SSL certificate to be trusted. :param proxies: (optional) The proxies dictionary to apply to the request. """ conn = self.get_connection(request.url, proxies) self.cert_verify(conn, request.url, verify, cert) url = self.request_url(request, proxies) self.add_headers(request) chunked = not (request.body is None or 'Content-Length' in request.headers) if isinstance(timeout, tuple): try: connect, read = timeout timeout = TimeoutSauce(connect=connect, read=read) except ValueError as e: # this may raise a string formatting error. err = ("Invalid timeout {0}. Pass a (connect, read) " "timeout tuple, or a single float to set " "both timeouts to the same value".format(timeout)) raise ValueError(err) else: timeout = TimeoutSauce(connect=timeout, read=timeout) try: if not chunked: resp = conn.urlopen( method=request.method, url=url, body=request.body, headers=request.headers, redirect=False, assert_same_host=False, preload_content=False, decode_content=False, retries=self.max_retries, timeout=timeout ) # Send the request. else: if hasattr(conn, 'proxy_pool'): conn = conn.proxy_pool low_conn = conn._get_conn(timeout=DEFAULT_POOL_TIMEOUT) try: low_conn.putrequest(request.method, url, skip_accept_encoding=True) for header, value in request.headers.items(): low_conn.putheader(header, value) low_conn.endheaders() for i in request.body: low_conn.send(hex(len(i))[2:].encode('utf-8')) low_conn.send(b'rn') low_conn.send(i) low_conn.send(b'rn') low_conn.send(b'0rnrn') # Receive the response from the server try: # For Python 2.7+ versions, use buffering of HTTP # responses r = low_conn.getresponse(buffering=True) except TypeError: # For compatibility with Python 2.6 versions and back r = low_conn.getresponse() resp = HTTPResponse.from_httplib( r, pool=conn, connection=low_conn, preload_content=False, decode_content=False ) except: # If we hit any problems here, clean up the connection. # Then, reraise so that we can handle the actual exception. low_conn.close() raise except (ProtocolError, socket.error) as err: raise ConnectionError(err, request=request) except MaxRetryError as e: if isinstance(e.reason, ConnectTimeoutError): # TODO: Remove this in 3.0.0: see #2811 if not isinstance(e.reason, NewConnectionError): raise ConnectTimeout(e, request=request) if isinstance(e.reason, ResponseError): raise RetryError(e, request=request) raise ConnectionError(e, request=request) except ClosedPoolError as e: raise ConnectionError(e, request=request) except _ProxyError as e: raise ProxyError(e) except (_SSLError, _HTTPError) as e: if isinstance(e, _SSLError): raise SSLError(e, request=request) elif isinstance(e, ReadTimeoutError): raise ReadTimeout(e, request=request) else: raise adapters.py Size 5 font. This is the definition of send() m ethod. Over 100 lines long and it can’t fit this slide. Exercise left to reader to read thru this send() m ethod.
- 59. """ requests.adapters ~~~~~~~~~~~~~~~~~ This module containsthe transport adapters that Requests uses to define and maintain connections. """ import os.path import socket from .models import Response from .packages.urllib3.poolmanager import PoolManager, proxy_from_url from .packages.urllib3.response import HTTPResponse from .packages.urllib3.util import Timeout as TimeoutSauce from .packages.urllib3.util.retry import Retry from .compat import urlparse, basestring from .utils import (DEFAULT_CA_BUNDLE_PATH, get_encoding_from_headers, prepend_scheme_if_needed, get_auth_from_url, urldefragauth, select_proxy) from .structures import CaseInsensitiveDict from .packages.urllib3.exceptions import ClosedPoolError from .packages.urllib3.exceptions import ConnectTimeoutError from .packages.urllib3.exceptions import HTTPError as _HTTPError from .packages.urllib3.exceptions import MaxRetryError from .packages.urllib3.exceptions import NewConnectionError from .packages.urllib3.exceptions import ProxyError as _ProxyError from .packages.urllib3.exceptions import ProtocolError from .packages.urllib3.exceptions import ReadTimeoutError from .packages.urllib3.exceptions import SSLError as _SSLError from .packages.urllib3.exceptions import ResponseError from .cookies import extract_cookies_to_jar from .exceptions import (ConnectionError, ConnectTimeout, ReadTimeout, SSLError, ProxyError, RetryError) from .auth import _basic_auth_str DEFAULT_POOLBLOCK = False DEFAULT_POOLSIZE = 10 DEFAULT_RETRIES = 0 DEFAULT_POOL_TIMEOUT = None the imports at top of requests/adapters.py urllib3 is imported here adapters.py
- 60. def send(self, request,stream=False, timeout=None, verify=True, cert=None, proxies=None): … import pytest pytest.set_trace() return self.build_response(request, resp) Let’s place a debugger in adapters.py and run the same unit test again. py.test test_requests.py::TestRequests::test_DIGEST_HTTP_200_OK_GET Run this same unit test on command line adapters.py
- 61. Use pytest debuggerto see output of send() method [48] > /Users/susantan/Projects/requests/requests/ adapters.py(455)send() -> return self.build_response(request, resp) (Pdb++) request.url ‘http://127.0.0.1:58948/digest-auth/auth/user/pass' (Pdb++) resp <requests.packages.urllib3.response.HTTPResponse object at 0x102c15110> (Pdb++) our_version_of_response_object = self.build_response(request, resp) (Pdb++) our_version_of_response_object.json() {u'authenticated': True, u'user': u’user'} (Pdb++) our_version_of_response_object.status_code 200
- 62. Goal for today— Figure out how this code snippet works >>> r = requests.get('https://api.github.com/ user', auth=('user', 'pass')) >>> r.status_code 200 >>> r.headers['content-type'] 'application/json; charset=utf8' >>> r.encoding 'utf-8' >>> r.text u'{"type":"User"...' >>> r.json() {u'private_gists': 419, u'total_private_repos': 77}
- 64. In summary, howdoes “request.get()” work?
- 65. def test_DIGEST_HTTP_200_OK_GET(self, httpbin): auth= HTTPDigestAuth('user', 'pass') url = httpbin('digest-auth', ‘auth', 'user', 'pass') r = requests.get(url, auth=auth) assert r.status_code == 200 r = requests.get(url) assert r.status_code == 401 s = requests.session() s.auth = HTTPDigestAuth('user', 'pass') r = s.get(url) assert r.status_code == 200 test_requests.py
- 66. def request(method, url,**kwargs): with sessions.Session() as session: return session.request(method=method, url=url, **kwargs) api.py This is the request method This is the get method def get(url, params=None, **kwargs): kwargs.setdefault('allow_redirects', True) return request('get', url, params=params, **kwargs)
- 67. def request(self, method,url, params=None, data=None, headers=None, cookies=None, files=None, auth=None, timeout=None, allow_redirects=True, proxies=None, hooks=None, stream=None, verify=None, cert=None, json=None): # Create the Request. req = Request( method = method.upper(), url = url, headers = headers, files = files, data = data or {}, json = json, params = params or {}, auth = auth, cookies = cookies, hooks = hooks, ) prep = self.prepare_request(req) proxies = proxies or {} settings = self.merge_environment_settings( prep.url, proxies, stream, verify, cert ) # Send the request. send_kwargs = { 'timeout': timeout, 'allow_redirects': allow_redirects, } send_kwargs.update(settings) resp = self.send(prep, **send_kwargs) return resp sessions.py What’s happening in this code? 1. create request 2. create prepare request object “prep” 3. send request 4. return response1 2 3 4 ✓ ✓ ✓ ✓
- 68. A mental mapof files and associated function calls adapters.py sessions.py models.py api.py File names test_requests.py request(), get(), session.request() class Request(), class PreparedRequest() class Request(), prepare_request(), send() send() method or class names test_DIGEST_HTTP_200_OK_GET()
- 69. No walkthrough ofa codebase is the same for any person. ie: skip reading any unit test. In [4]: import requests In [4]: resp = requests.post('http://httpbin.org/post', data={'name':'Susan'}) [14] > /Users/susantan/Projects/requests/requests/ adapters.py(346)send() -> conn = self.get_connection(request.url, proxies) (Pdb++) l 341 """ 342 343 import pytest 344 pytest.set_trace() 345 346 -> conn = self.get_connection(request.url, proxies) 347 348 self.cert_verify(conn, request.url, verify, cert) 349 url = self.request_url(request, proxies) 350 self.add_headers(request) 351 (Pdb++) dir() ['cert', 'proxies', 'pytest', 'request', 'self', 'stream', 'timeout', 'verify'] Set breakpoints!
- 70. • What didwe do? We took a code snippet (“requests.get(url)”)& its unit test and followed it through. • We really know “requests.get(url)” works in great depth. • We chose a small code snippet to guide our walkthrough. • We set breakpoints, read unit tests, & read some docs. • Ask LOTS of questions & find the answers. Be curious. Takeaways
- 71. • Ideally, getcontact info of core devs & get in touch with them. • Ask on mailing list, chat, IRC, Twitter, in-person. • Use git blame to see who wrote that section. • File an issue for better docs, better docstrings & code comments. What to do when you get really stuck on figuring out codebase?
- 72. Related Past Talkon Reading Code • RailsConf 2014 - Reading Code Good by Saron Yitbarek @saronyitbarek: about experiences with a weekly code club that would read a code base as a group
- 73. Hope this helps.Thanks for attending! Where to reach me: @ArcTanSusan on Twitter, IRC San Francisco, CA