Unit-IV Strings.pptx

Unit-IV Strings
Subject: Programming and Problem Solving
TSSM’S
Bhivarabai Sawant College of
Engineering & Research,
Narhe, Pune -41
Prof. N. B. Pokale

Syllabus
Strings and Operations – concatenation, appending,
multiplication and slicing.
Strings are immutable, strings formatting operator,
built in string methods and functions
Slice operation
ord() and chr() functions
in and not in operators
Comparing strings
Iterating strings
the string module
PPS Unit-III Functions and Modules 2

Introduction
The Python string data type is a sequence made up
of one or more individual characters, where a
character could be a letter, digit, whitespace, or any
other symbol.
Python treats strings as contiguous series of
characters delimited by single, double or even triple
quotes.
Python has a built-in string class named “str” that
has many useful features.
Different ways of creating strings.

Examples
Name=“India”
Graduate=‘N’
Country=name
Nationality=str(“Indian”)
 Here, name, graduate, country, and nationality are all
string variables.
Indexing:
 Individual characters in a string are accessed using the
subscript ([]) operator.
 The expression in brackets is called an index.
 The index specifies a member of an ordered set and in
this case it specifies the character we want to access
from the given set of characters in the string.

 The index of the first character is 0 and that of the last
character is n-1 where n is the number of characters in
the string.
 If you try to exceed the bounds (below 0 or above n-1),
then an error is raised.
Traversing a String:
 A string can be traversed by accessing character(s)
from one index to another.
 Example
#Program to demonstrate string traversal using indexing
message="Hello!"
index=0
for i in message:
print("message[",index,"] =",i)
index+=1

 Example2
#Program to demonstrate an expression used as an index of a
string
str = "Hello, welcome to the world of Python"
i=2
print(str[i])
print(str[i*3+1]) # index is an expression that evalueates to an
integer
 String index must be an integer
 Example 3
str="Hello, welcome to the world of Python"
print(str['o'])
Output:
TypeError: string indices must be integers

1. String Operations
Concatenating:
 The word concatenate means to join together.
 Python allows you to concatenate two string using +
operator.
 Example 1
#Program to concatenate two strings using + operator
str1="Hello "
str2="World"
str3=str1+str2
print("The concatenated string is:",str3)
Output:
The concatenated string is: Hello World

Appending:
 Append means to add at the end.
 In Python we can add one string at the end of another
string using the += operator.
 Example 1:
#Program to append a string using += operator
str="Hello, "
name=input("Enter your name :")
str+=name
str+="Welcome to Python Programming."
print(str)
Output:
Enter your name :Sarthak
Hello, Sarthak Welcome to Python Programming.

Multiplying Strings
 We can use the * operator to repeat a string n number
of times.
 Example 1:
#Program to repeat a string using * operator
s="Hello"
print(s*3)
Output:
HelloHelloHello

str() function:
 The str() function is used to convert values of any other
type into string type.
 This helps the programmer to concatenate a string with
any other data which is otherwise not allowed.
 Example 1:
s1="Hello"
var=7
s2=s1+var
print(s2)
Output:
TypeError: can only concatenate str (not "int") to str

 Example 2:
s1="Hello"
var=7
s2=s1+str(var)
print(s2)
Output:
Hello7

Printing on the same line (end=“ ”):
 The print statement prints one or more literals or
values in a new line.
 If you don’t want to print on a new line then, add end
statement with a separator like whitespace, comma,
etc.
Example 1:
print("Hello")
print("World")
Output:
Hello
World
Example 2:
print("Hello",end=" ")
print("World")
Output:
Hello World

Raw String:
 A raw string literal which is prefixed by an ‘r’ passes all
the characters as it is.
 They are not processed in any special way, not even
the escape sequences.
 Program to print a raw string
print("Hello")
print(r"nWorld")
Output:
Hello
nWorld
The ‘u’ prefix is used to write Unicode string literals

2. Strings are Immutable
Python strings are immutable which means that
once created they cannot be changed.
Whenever you try to modify an existing string
variable, a new string is created.
Use of id()
 Every object in Python is stored in memory.
 We can find out whether two variables are referring to
the same object or not by using the id().
 The id() returns the memory address of that object.

Example :
str1="Hello"
print("Str1 is: ",str1)
print("ID of str1 is : ",id(str1))
str2="World"
print("Str2 is: ",str2)
str1+=str2
print("Str1 after concatenation is :",str1)
str3=str1
print("Str3 =",str3)
print("ID of str3 is: ",id(str3))

 Output:
Str1 is: Hello
ID of str1 is : 59465312
Str2 is: World
ID of str2 is : 59465408
Str1 after concatenation is : HelloWorld
ID of str1 is : 59457432
Str3 = HelloWorld
ID of str3 is: 59457432
 From the output, it is very clear that str1 and str2 are
two different string objects with different values and
have different memory address.
 When we concatenate str1 and str2, a new string is
created because strings are immutable in nature.

 You can check this fact by observing the current and
previous address of str1.
 Finally, we create a new string variable str3 and
initialize it with str1. Since they both point to the same
value, their address is exactly same.
Example to show strings are immutable
 Example
str="Hi"
str[0]='B'
print(str)
Output:
str[0]='B'
TypeError: 'str' object does not support item assignment

If we want to make any kind of changes you must
create a new string
 Example
str="Hi"
new_str="Bi"
print("old string = ",str)
print("New string = ",new_str)
Output:
old string = Hi
New string = Bi
You cannot delete or remove characters from a
string. However, we can delete the entire string
using the keyword del.

3. String Formatting Operator
 This string formatting operator is one of the exciting
features of Python.
 The % operator takes a format string on the left (that
has %d, %s, etc.) and the corresponding values in a
tuple on the right.
 The format operator, % allows users to construct
strings, replacing parts of the strings with the data
stored in variables.
 The syntax for the string formatting operator is:
“<FORMAT>”%(<VALUES>)
 The statement begins with a format string consisting of
a sequence of characters and conversion specifications.

 Conversion specifications start with a % operator and
can appear anywhere within the string.
 Following the format string is a % sign and then a set of
values, one per conversion specification, separated by
commas and enclosed in parenthesis.
 If there is a single value then parenthesis is optional.
 Example 1: Program to use format sequences while
printing a string.
name= "Aarish"
age=8
print("Name = %s and Age = %d"%(name,age))
print("Name = %s and Age = %d"%("Anika",6))
Output:
Name = Aarish and Age = 8
Name = Anika and Age = 6

 In the output we can see that %s has been replaced by
a string and %d has been replaced by an integer value.
 The values to be substituted are provided at the end of
the line – in brackets prefixed by %.
 You can either supply these values directly or by using
variables.
 The number and type of values in the tuple should
match the number and type of format sequences or
conversion specifications in the string, otherwise an
error is returned.
>>> '%d%f%s'%(100,23.45)
TypeError: not enough arguments for format string
>>> "%f"%"abc“
TypeError: must be real number, not str

Format Symbol Purpose
%c character
%d or %i Signed decimal integer
%s string
%u Unsigned decimal integer
%o Octal integer
%x or %X Hexadecimal integer (x for lower case characters a-f
and X fo upper case characters A-F)
%e or %E Exponential notation
%f Floating point number
%g or %G Short numbers in floating point or exponential notation
Table : Formatting symbols

 Program to display powers of a number without using
formatting characters.
i=1
print("iti**2ti**3ti**4ti**5ti**6ti**7ti**8ti**9ti**10")
while i<=10:
print(i, 't', i**2, 't', i**3, 't', i**4, 't', i**5,
't', i**6, 't', i**7, 't', i**8, 't', i**9, 't', i**10)
i+=1
 The output looks weird and unorganized
 The above program prints a table that prints powers of
numbers from 1 to 10. Tabs are used to align the
columns of values.
 We see that as the digits increases the columns
becomes misaligned.

 Program to display powers of numbers using
formatting characters.
i=1
print("%-4s%-5s%-7s%-8s%-13s%-15s%-17s%-19s%-21s%-23s"%
('i','i**2','i**3','i**4','i**5','i**6','i**7','i**8','i**9','i**10'))
while i<=10:
print("%-4d%-5d%-7d%-8d%-13d%-15d%-17d%-19d%-21d%-23d"%
(i, i**2, i**3, i**4, i**5, i**6, i**7, i**8, i**9, i**10))
i+=1
 The – after each % in the conversion string indicates
left justification.
 The numerical values specify the minimum length.
Therefore, %-15d means it is a left justified number
that is at least 15 characters wide.

4. Build-in String Methods and Functions
 Strings are an example of Python objects.
 An object is an entity that contains both data (the
actual string itself) as well as functions to manipulate
that data.
 These functions are available to any instance (variable)
of the object.
 Python supports many built-in methods to manipulate
strings.
 A method is just like a function.
 The only difference between a function and method is
that a method is invoked or called on an object.

 For example, if the variable str is a string, then you can
call the upper() method as str.upper() to convert all the
characters of str in uppercase.

Function Usage Example
startswith (prefix, beg,
end)
Checks if string starts with
prefix; if so, it returns True
and False otherwise. You
can either set beg=0 and end
equal to the length of the
message to search entire
string or use any other value
to search a part of it.
str ="The world is beautiful"
print(str.startswith("Th", 0,
len(str)))
Output:
True
find(str, beg, end)
Checks if str is present in
string. If found it returns the
position at which str occurs
in string, otherwise returns -
1. You can either set beg=0
and end equal to the length
of the message to search
entire string or use any other
value to search a part of it
message = "She is my best
friend"
print(message.find("my",0,l
en(message)))
Output:
7

index(str, beg, end)
Same as find but
raises an exception if
str is not found.
message="She is my
best friend"
print(message.index("my
",0,len(message)))
Output:
7
rfind(str, beg, end)
Same as find but
starts searching from
the end.
str="Is this your bag?"
print(str.rfind("is",0,len(st
r)))
Output:
5
rindex(str, beg, end)
Same as index but
start searching from
the end and raises an
exception if str is not
found
str="Is this your bag?"
print(str.rindex("is",0,
len(str)))
Output:
5

isalnum()
Returns True if string has at
least 1 character and every
character is either a number
or an alphabet and False
otherwise
message=“JamesBond007”
print(message.isalnum())
Output:
True
isalpha()
character is an alphabet and
False otherwise.
message="JamesBond"
print(message.isalpha())
isdigit()
Returns True if string
contains only digits and
False otherwise.
message="007"
print(message.isdigit())
islower()
character is a lowercase
alphabet and False
otherwise.
message="hello"
print(message.islower())
Output:
True

Method / Function Usage Example
isspace()
Returns True if string
contains only whitespace
characters and False
otherwise
message=" "
print(message.isspace())
Output:
True
isupper()
character is an upper case
alphabet and False
otherwise.
message="HELLO"
print(message.isupper())
Output:
True
len(string)
Returns the length of the
string.
str="Hello"
print(len(str))
Output:
5
ljust(width[, fillchar])
Returns a string left-justified
to a total of width columns.
Columns without characters
are padded with the
character specified in the
fillchar argument.
str="Hello"
print(str.ljust(20,"*"))
Output:
Hello***************

rjust(width [,fillchar])
Returns a string right-justified to a
total of width columns. Columns
without characters are padded
with the character specified in the
fillchar argument.
str="Hello"
print(str.rjust(20,'*'))
Output:
***************Hello
zfill(width)
Returns string left padded with
zeros to a total of width
characters. It is used with
numbers and also retains its sign
(+ or - )
str="12345"
print(str.zfill(20))
Output:
00000000000000012345
lower()
Converts all characters in the
string into lowercase.
str="HELLO"
print(str.lower())
Output:
hello
upper()
Converts all characters in the
string into uppercase.
str="hello"
print(str.upper())
Output:
HELLO

Method /
Function
Usage Example
lstrip()
Removes all leading whitespace in
string.
str=" Hello"
print(str.lstrip())
Output:
Hello
rstrip()
Removes all trailing whitespace in
string.
str=" Hello "
print(str.rstrip()+"World")
Output:
HelloWorld
strip()
Removes all leading and trailing
whitespace in string.
str=" Hello "
print(str.strip()+"World")
Output:
HelloWorld
max(str)
Returns the highest alphabetical
character(having highest ASCII value)
from the string str.
str="Wheelz"
print(max(str))
Output: z
min(str)
Returns the lowest alphabetical
character(having lowest ASCII value)
from the string str.
str="Wheelz"
print(min(str))
Output:
W

Method /
Function
Usage Example
replace(old,
new [, max]
)
Replaces all or max (if given)
occurrences of old in string with new.
str="Hello Hello Hello"
print(str.replace('H', 'h'))
str="AAAABBBBB"
print(str.replace("A",'a',2))
Output:
hello hello hello
aaAABBBBB
title() Returns string in title case.
str="hello, How r u?"
print(str.title())
Output:
Hello, How R U?
swapcase()
Toggles the case of every character
(uppercase character becomes
lowercase and vice versa).
str="The World Is Beautiful"
print(str.swapcase())
Output:
tHE wORLD iS bEAUTIFUL

split(delim)
Returns a list of substrings separated by
the specified delimiter. If no delimiter is
specified then by default it splits strings
on all whitespace characters.
str="Hello how r u?"
print(str.split(" "))
Output:
['Hello', 'how', 'r', 'u?']
join(list)
It is just opposite of split. The function
joins a list of strings using the delimiter
with which the function is invoked.
l=['a', 'b', 'c', 'd']
print('#'.join(l))
output:
a#b#c#d
isidentifier()
Returns True if the string is a valid
identifier.
str="#hello"
print(str.isidentifier())
Output:
False
enumerate(str)
Returns an enumerate object that lists
the index and value of all the characters
in the string as pairs.
str="Hello"
print(list(enumerate(str)))
Output:
[(0, 'H'), (1, 'e'), (2, 'l'), (3,
'l'), (4, 'o')]

 Note that the strip() function when used with a string
argument will strip (from both ends) any combination
of the specified characters in the string.
 Program – to demonstrate strip method on a string
object.
str="hello hello olleh"
print(str.strip("he"))
Output:
llo hello oll
format() function:
 The format() function used with strings is a very
versatile and powerful function used for formatting
string.

 Format strings have curly braces {} as placeholders or
replacement fields which gets replaced.
 We can even use positional arguments or keyword
arguments to specify the order of fields that have to be
replaced
 Example – Program to demonstrate format() function.
str1="{},{} and {}".format('Sun','Moon','Stars')
print(str1)
print("{1}, {0} and {2}".format('Sun','Moon','Earth'))
print("{c},{b} and {a}".format(b='Sun',a='Moon',c='Earth'))
print("{} and {}".format(12.333,345.1111))
Output:
Sun,Moon and Stars
Moon, Sun and Earth
Earth,Sun and Moon
12.333 and 345.1111

5. Slice Operation
 A substring of a string is called a slice.
 The slice operation is used to refer to sub-parts of
sequences and strings.
 You can take subset of a string from the original string
by using [] operator also known as slicing operator.
 Let us consider the index of characters in a string.
P Y T H O N
0 1 2 3 4 5
-6 -5 -4 -3 -2 -1
Index from
the start
Index from
the end

 The syntax of slice operation is
s[start : end] , where start specifies the beginning index
of the substring and end-1 is the index of the last
character.
 Note: Omitting either start or end index by default
takes start or end of the string. Omitting both means
the entire string.

 Example: Program to demonstrate slice operation on
string objects.
str="PYTHON"
print("str[1:5] = ",str[1:5]) #characters starting at index 1 and
extending up to but not including index 5
print("str[ : 6]=",str[ : 6]) #defaults to the start of the string
print("str[1 : ] =",str[1: ]) #defaults to the end of the string
print("str[ : ] =",str[ :]) # defaults to the entire string
print("str[1:20] =",str[1:20]) #an index that is too big is truncated
down to length of the string
Output:
str[1:5] = YTHO
str[ : 6]= PYTHON
str[1 : ] = YTHON
str[ : ] = PYTHON
str[1:20] = YTHON

 Python gives you the flexibility to either access a string
from the first character or from the last character.
 If we access the string from the first character then we
use a zero based index ,but when doing it backward the
index starts with -1.
Note: Python uses negative numbers to access the
characters at the end of the string. Negative index
numbers count back from the end of the string.
 Example – Program to understand how characters in a
string are accessed using negative indexes.
str="PYTHON"
print("str[-1]=", str[-1]) # last character is accessed
print("str[-6] =",str[-6]) # first character is accessed

print("str[-2:]=",str[-2:]) # second last and last character are accessed
print("str[:-2] = ",str[:-2]) #all characters upto but not including second
last character
print("str[-5:-2] =",str[-5:-2]) # characters from second upto second
last are accessed.
Output:
str[-1]= N
str[-6] = P
str[-2:]= ON
str[:-2] = PYTH
str[-5:-2] = YTH
 Elements are accessed from left towards right.
• Note: when using negative index numbers, start with
the lower number first as it occurs earlier in the string.

5.1 Specifying Stride while Slicing Strings
 In the slice operation, you can specify a third argument
as the stride, which refers to the number of characters
to move forward after the first character is retrieved
from the string.
 The default value of stride is 1.
 Example- Program to use slice operation with stride
str="Welcome to the world of Python"
print("str[2:10] = ",str[2:10]) # default stride is 1
print("str[2:10:1] = ",str[2:10:1]) # same as stride =1
print("str[2:10:2] = ",str[2:10:2]) # skips every alternate
character
print("str[2:10:4] = ",str[2:10:4]) #skips to every fourth character

Output:
str[2:10] = lcome to
str[2:10:1] = lcome to
str[2:10:2] = loet
str[2:10:4] = le
 Note that even the whitespace characters are skipped
as they are also a part of the string.
 If you omit the first two arguments and specify the
third one, then the entire string is used in steps.
 Example- Program to demonstrate slice operation with
just last(positive) argument.
print("str[::3] = ",str[::3])
Output: str[::3] = WceohwloPh

 You can also specify a negative value for the third
argument.
This is especially useful to print the original string
in reverse order by setting the value of stride to -1.
 Example- Program to demonstrate slice operation with
just last(negative) argument.
print("str[::-1] = ",str[::-1])
Output:
str[::-1] = nohtyP fo dlrow eht ot emocleW
 Example – Program to print the string in reverse
skipping to every third character.
print("str[::-3] = ",str[::-3])
Output: str[::-3] = nt r ttml

6. ord() and chr() Functions
 The ord() function returns the ASCII code of the character
and the chr() function return character represented by an
ASCII number.
 Example s –
ch='A'
print(ord(ch))
print(chr(102))
print(chr(122))
print(ord('1'))
Output:
65
f
z
49

7 in And not in Operators
 in and not in operators can be used with strings to
determine whether a string is present in another string.
 Therefor, the in and not in operator are also known as
membership operators.
 Example1-
str1="Welcome to the world of Python"
str2="world"
if str2 in str1:
print("found")
else:
print("not found")
print('P' in "Python")
Output: found
True

 Example 2 –
str1="Welcome to Python"
str2="World"
if str2 not in str1:
print("Ok")
else:
print("not ok")
print('x' not in "Python")
Output:
Ok
True
 We can also use the in and not in operators to check
whether a character is present in a word.

>>> 'u' in "stars"
False
>>> 'v' not in 'Success'
True
>>> 'vi' in 'victory'
True
While using the in and
not in operators,
remember that a string is
a substring of itself.
>>> 'world' in 'world'
True
>>> 'a' in 'a'
True
>>> 'Hello Friends' in "Hello
Friends"
True

8 Comparing Strings
 Python allows you to compare strings using relational
(or comparison) operators such as >, <, <=, etc.
 These operators compare the strings by using the
lexicographical order i.e. using ASCII value of the
characters.
 The ASCII values of A-Z is 65-90 and ASCII for a-z is 97-
122.
 This means that book is greater than Book because the
ASCII value of ‘b’ is 98 and ‘B’ is 66.

Table : String Comparison Operators and their description.
Operator Description Example
== If two strings are equal, it returns True. >>> "Abc"=="Abc"
True
!= or <> If two strings are not equal, it returns True. >>> "ABC" != "abc"
True
> If the first string is greater than the second, it
returns True.
>>> "abc">"ABC"
True
< If the second string is greater than the first, it
returns True.
>>> "ABC"<"abc"
True
>= If the first string is greater than or equal to the
second, it returns True.
>>> 'xyz'>='xyz'
True
<= If the second string is greater than or equal to
the first, it returns True.
>>> 'xyz'<='xyz'
True

9 Iterating String
 String is a sequence type (sequence of characters).
 We can iterate trough the string using for loop.
 Example – Program to iterate a given string using for
loop
str="Welcome to Python"
for i in str:
print(i, end=" ")
Output:
W e l c o m e t o P y t h o n
 In the above program, the for loop executes for every
character in str.
 The loop starts with the first character and automatically ends
when the last character is accessed.

 You can iterate through the string using while loop
also.
 Example – Program to iterate a given string using while
loop.
str="Welcome to Python"
index=0
while index<len(str):
print(str[index], end= " ")
index+=1
Output:
W e l c o m e t o P y t h o n

 We can iterate through a string either using an index or
by using each character in the string.
• Uses character to iterate
# uses character to iterate
def copy(str):
new_str=''
for i in str:
new_str+=i
return new_str
str=input("Enter a string:")
print("The copied string is
:",copy(str))
Output:Enter a string:Welcome
The copied string is: Welcome
# uses index of character to iterate
def copy(str):
new_str=''
for i in range(len(str)):
new_str+=str[i]
return new_str
str=input("Enter a string:")
print("The copied string is:
",copy(str))
Ouput:
Enter a string:Welcome
The copied string is: Welcome

10 The String Module
 The string module consists of a number of useful
constants, classes, and functions.
 These functions are used to manipulate strings.
String Constants:
 string.ascii_letters: Combination of ascii_lowercase
and uppercase constants.
 string.ascii_lowercase : Refers to all lowercase letters
from a-z.
 string.ascii_uppercase: Refers to all uppercase letters,
A-Z.
 string.digits: Refers to digits 0-9

 string.hexdigits: Refers to hexadecimal digits, 0-9, a-f
and A-F.
 string.lowercase: A string that has all the characters
that are considered lowercase letters.
 string.octtdigits: Refers to ocatl digits , 0-7
 string.punctuation : String of ASCII characters that are
considered to be punctuation characters.
 string.printable: String of printable characters which
includes digits, letters, punctuation, and whitespace.
 string.uppercase: A string that has all characters that
are considered uppercase letters.
 string.whitespace: A string that has all characters that
are considered whitespace like space, tab, linefeed,
return, form-feed, and vertical tab.

 Program that uses different methods (upper, lower, split,
join, count, replace, and find) on string object.
print("Uppercase -", str.upper())
print("Lowercase -", str.lower())
print("Split - ", str.split())
print("Join -",'-'.join(str.split()))
print("Replace -", str.replace("Python","Java"))
print("Count of o -",str.count('o'))
print("Find of -",str.find("of"))
Output:
Uppercase - WELCOME TO THE WORLD OF PYTHON
Lowercase - welcome to the world of python
Split - ['Welcome', 'to', 'the', 'world', 'of', 'Python']
Join - Welcome-to-the-world-of-Python
Replace - Welcome to the world of Java
Count of o - 5
Find of - 21

 To see the contents of the string module, use the dir()
with the module name as an argument.
>>> import string
>>> dir(string)
['Formatter', 'Template', '_ChainMap', '_TemplateMetaclass',
'__all__', '__builtins__', '__cached__', '__doc__', '__file__',
'__loader__', '__name__', '__package__', '__spec__', '_re',
'_string', 'ascii_letters', 'ascii_lowercase', 'ascii_uppercase',
'capwords', 'digits', 'hexdigits', 'octdigits', 'printable',
'punctuation', 'whitespace']

 To know the details of a particular item, you can use
the type command. The function type() takes as an
argument the module name followed by the dot
operator and the item name.
 Example 1
import string
print(type(string.digits))
Output:
<class 'str'>
 Example 2
import string
print(type(string.ascii_letters))
Output:
<class 'str'>

 To find the details of a particular function, you can print its
documentation using the docstring through __doc__
attribute.
 Program to print the docstring of an item in string module.
import string
print(string.__builtins__.__doc__)
Output:
dict() -> new empty dictionary
dict(mapping) -> new dictionary initialized from a mapping object's
(key, value) pairs
dict(iterable) -> new dictionary initialized as if via:
d = {}
for k, v in iterable:
d[k] = v
dict(**kwargs) -> new dictionary initialized with the name=value pairs
in the keyword argument list. For example: dict(one=1, two=2)

 You can even use the help() to print the details of a
particular item in the string module.
str=“Hello”
print(help(str.isalpha))
Output:
Help on built-in function isalpha:
isalpha() method of builtins.str instance
Return True if the string is an alphabetic string, False
otherwise.
A string is alphabetic if all characters in the string are
alphabetic and there
is at least one character in the string.
None

Working with Constants in String Module:
 We can use the constants defined in the string module
along with the find() function to classify characters.
 For example, if find(lowercase, ch) returns a value
except -1, then it means that ch must be a lowercase
character.
 An alternate way to do the same job is to use the in
operator or even the comparison operation.
 First Way
import string
print(str.find(string.ascii_lowercase,'g')!=-1)
Output:
True

 Second way
import string
print('g' in string.ascii_lowercase)
Output:
True
 Third way
ch='g'
print('a'<=ch<='z')
Output:
True
 Note: type() shows the type of an object and the dir()
shows the available methods.

 Another very useful constant defined in the string
module is whitespace.
 When you write, print(string.whitespace) then all the
characters that moves the cursor ahead without
printing anything are displayed.
 These whitespace characters include space, tab, and
newline characters.
You can even use the dir() with a string object or a
string variable
str="hello"
print(dir(str))

Copying and Pasting Strings with the Pyperclip
Module
 The peperclip module in Python has copy() and paste()
functions that can send text to and receive text from
the computer’s clipboard.
 Copying the output of your program to the clipboard
makes it easy to paste it to an email, word processor,
or other software.
import pyperclip
pyperclip.copy("Welcome to Python")
print(pyperclip.paste())

Unit-IV Strings.pptx

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