python and web for data science prfrograminh

Python and Web
Programming
November 21, Unit 8

Web Scripts
• Programs that generate web pages are often
called web scripts or CGI scripts
• Like using XSL to transform an XML file into an
HTML file, we can use web scripts to create web
pages for us
• Why use web scripts?
– Allows use to dynamically generate web pages
• These web pages are created upon request
– Standard HTML files stored on a server are called
static web pages or static files
• They don’t really change (unless we edit the HTML)

Creating Web Pages
• We can create web pages using a script in
many different languages
• Obviously, we can use Python (since that’s
what we’re learning)
• Other common languages include:
– Perl
– PHP
– ASP

Simple Page in Python
• Creating a simple web page in Python is very
similar to how it was done using XSL
• Basically, the Python program will need to output
the HTML we need for our page
• To do this, we’ll use a series of print statements
• The basic things we need are:
– Header information (text/html)
– A blank line
– <html>, <head>, <title>,<body>, HTML content, and
closing tags

Simple Python Script
print “Content-type: text/html”
print
print ”<html><head>”
print “<title>Python Example</title>”
print ”</head><body>”
print “<h1>Python is fun</h1>”
print “<p> Python made this page</p>”
print “</body></html> “

Header Information
• print “Content-type: text/html”
• This produces the header information for our
web page
• Basically the purpose of this is to tell the browser
which type of information is going to be sent
– Indicates the MIME type
• When we put a python script online, it has the
extension “.py”
– Browser needs to know that HTML is coming
• Why the blank line after the header?
– Indicates the start of the HTML

Triple-Quoted Strings
• When we create web pages with Python
we can dynamically change parts of the
page
– But large portions of the page may be static
• Instead of having multiple print statements
we can use fewer and enclose much of
our HTML in triple quoted strings “’
– Allows us to have line breaks where double
quotes do not in python

Triple-Quoted String Example
print
print ”””<html><head>
<title>Python Example</title>
</head><body>
<h1>Python is fun</h1>
<p> Python made this page</p>
<body></html> “””
• This produces the same output as the first example
Python script
• Allows us to copy and paste large chunks of HTML

Python Generated Web Pages
• The previous scripts are kind of pointless
to do with Python
– They actually create static web pages
– They don’t change
• But we can generate web pages that do
change
• A simple example is to include the current
time on a web page

Adding Time to a Web Page
import time
print
print “’<html><head><title>Time
Page</title></head>”’
print”<body><p>Right now, the time is <strong> “
print time.asctime(), “</strong></p>”
Print “</body></html>”

Output From Last Script
Content-type: text/html
<html><head><title>Time Page</title></head>
<body><p>Right now, the time is <strong>Tue
Nov 21 13:45:00 2005 </strong></p>
</body></html>

Running Python Scripts
• When we run this script locally, we see the
output from our script
– What we have on the last slide
– We don’t see the web page we wanted to create
• To get the page to display we need to upload it
to the cmpt165 server
– Our webpage will have the URL path of somepage.py
• We can test our use of the timeasc function by
running it in IDLE
– The output will show up in the window

raw_data vs. Forms
• Right now we’re using raw_data to get user input
• But if we’re using a web page, we have no
console for the user to enter data into
• Instead we’ll use forms
• Forms allow users to enter data into a web page
– This data is then sent back to the web script on the
web server
• We are familiar with forms
– We enter information into a form when we use a
search engine
– Purchase items online

Building a Basic Page with a Form
• The first thing we need is the <form> tag
• The <form> tag goes around the entire
form
– Does not affect the appearance of the page
– Just notes where the form begins and ends
– Just like writing standard HTML
• <form> needs an attribute called “action”
– This specifies the action to be taken when the
form is submitted

<form>, cont.
• The action attribute is very important
– Why have a form that does nothing?
• action specifies which script to run when
the form is submitted
• The value for action should be the URL of
the script
• <form action = “testScript.py”>
• <form action =
“someFolder/customerInfo.py”>

Adding Controls
• Controls are those elements which we are going
to add to the form
– Text fields
– Text areas
– Check boxes
– Radio Buttons
– Selectable Lists
– Submit button
• A form without controls is pointless
– There’s no user input!
• We are going to add controls using the <input>
tag

<input> Tag
• With the <input> tag we need to specify
two attributes:
– type
– name
• Type attribute specifies the type of control
• Name attribute gives a name to the control
so we can access the data in it later
– Like giving it a variable name

Type Attribute
• Again, the type attribute specifies the type
of control
• Some examples include:
– type =“text” - text box
– type =“checkbox” –check box
– type =“radio” –radio button
– type = “submit” –submit button
• Example:
<input type =“submit”…..

Name Attribute
• We have to have a name to access the
information in a particular portion of the form
– Very similar to naming variables
• It’s best if the name relates to the content of the
control and the control type
– Ex.
• A text box control which gets a customer name could have a
name= “customerName”
• A check box control which allows customer to select getting
product updates name=“checkUpdates”

Value Attribute
• Sometimes we’ll also want to add a value attribute
• The value attribute specifies the default value for that
control
• Ex.
– <input type=“text” value=“a textbox” name=“textbox1”/>
• “a textbox” would appear in the text box
• Checkboxes can use the checked property to indicate if
it should be checked by default
– <input type=“checkbox” checked=“checked”
name=“checkbox1”/>
– If checked=“checked” then the box will appear checked
– “checked” is the only value that the checked property can have

Other Useful Text Attributes
• size attribute indicates how wide the text
box should be
<input type = “text” name=“text1” size =“10”/>
– Size indicates how many characters, in this
case 10
• maxlength is just like size except that it
indicates the maximum number of
characters a text box will accommodate

Submit Type
• We have to have a way to send the form
information to the script that’s going to handle it
• To do this we can use a control with the type
“submit”
• It will show up as a button
• The value attribute will indicate the text which
should be displayed on the button
<input type=“submit” value=“Go”
name=“submitButton”/>

HTML Form Example
In class Example

What’s Next?
• So now we can create forms
• And users can enter information
• But how the heck do we use it?
• We are going to use CGI to take the
information from the form and process it
somehow
– We’ll get into this next class
• You’ll be using CGI to take order
information

Questions
• What you should know:
– What web scripts are
– How to create a webpage using Python
– How to use triple quoted strings
– How to write a form in HTML
• <form action=“someprogram.py”>
• <input>

python and web for data science prfrograminh

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