CBSE Class 11 Comprehensive Notes of Strings in Python with Questions

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Practice Questions of String in python
Strings in Python

What is String in Python?

Strings are contiguous series of characters enclosed in single or double quotes. Python doesn’t have any separate data type for characters so they are represented as a single character string. 

For eg: 

>>> s_name = “Amit” # s_name is a variable storing a string.  

>>>s = ‘a’  #String can also be enclosed in single  quotes

How to Create Strings in Python?

Creating strings: To create string enclose the character or sequence of character in Single or Double Quotes like shown below

>>> s_name = “Amit”  #String enclosed in double quotes

>>>s = ‘a’ # String enclosed in Single Quotes

We can also use str() function to create string: 

N = str () # This function will create an empty string 

name = str(1234) # This will create a variable name which store a string “1234” 

If we execute the following code: 

>>>print(name) 

Output will come 

1234

Traversing Strings in Python:

Traversing a String:   It means accessing all the elements of the string one by one using index value. 

St = “PYTHON” 

Strings in Python
St[1] = Y  St[5] = N St[-1] = N St[-6] = P 

Iterating through string using for loop: 

Traversing the strings in Python using for loop 

Strings in Python
Strings in Python

Operation of Strings in Python 

Strings in Python
Membership Operator : there are two membership
operators:
1. ‘in’ operator returns True if a substring
is present in main string
2. ‘not in’ operator returns True if a substring
is not present in main string.

str1 = “Welcome”
print(‘com’ in str1)
print(‘W’ in str1)

print(‘Wel’ not in str1)
OUTPUT

True
True
False
String Comparison : We can compare
the string using relational/comparison
operator like (>, <, >=, <=, ==, !=)

print(“amit” == “Amit”)
print(“amit” != “Amit”)
print(“blog” > “z”)
OUTPUT


False
True
False
Strings in Python
Strings in Python

NOTEStrings are immutable means that the content of the string cannot be changed 

We can not change the character in the String

Inbuilt Functions of Strings in Python: 

Function NameDescriptionCodeOutput
split()This function splits
the string into a list of
string on the basis of
delimiter 
str = ” I am Learning Python”
print(str.split())
[‘I’ , ‘am’ , ‘Learning’ , ‘Python’ ]
upper() This function converts
the string into uppercase 
str = ” I am Learning Python”
print(str.upper())
I AM LEARNING PYTHON
lower() This function converts the
string into lowercase 
str = ” I am Learning Python”
print(str.lower()
)
i am learning python
replace()  
This function replaces a
substring from the main
string.
As strings are immutable
so this function creates
a new string 
str = ” I am Learning Python”
newstr=str.replace (“Learning”,”Doing”)
print(newstr)
I am Doing Python
find() This function return the
index of substring in a
main string. 
str = “I am Learning Python”
print(str.find(‘am’))
2
len() This function returns the length of the string.str = “I am Learning Python”
print(len(str))
20
strip() This function is used to
remove leading
and trailing whitespace
from the string. 
str=” I am Learning Python”
print(len(str))
strnew=str.strip()
print(len(strnew))
25
20
count() This function counts
the number of
occurrences of a substring
in main string 
str=”I am Learning Python”
print(str.count(‘a’))
print(str.count(‘n’))
2
3
capitalize() This function converts
the first alphabet
of the string to upper
case and all other
alphabets in small case 
str=”I am Learning Python”
print(str.capitalize())
I am learning python
index() This function returns
the lowest index
of substring in a string. 
str=”I am Learning Python”
print(str.index(‘a’))
2
isalnum() This function returns
True if it’s made of
alphanumeric characters
only. If there is one
space in a string,
this function will
return False. 
str=”I am Learning Python”
print(str.isalnum())


str=”IamLearningPython”
print(str.isalnum())
False (#it contain spaces)

True
isdigit()  
This function returns
True if all the characters
in the string are digits
otherwise False. 
str=”12345678″
print(str.isdigit())



str=”12345678A”
print(str.isdigit())
True(#only digits)



False(#contain alphabet)
islower() This function returns
True if all the characters
in the string are in lower case
str=”I am Learning Python”
print(str.islower())




str=”i am learning python”
print(str.islower())
False(#contain upper case alphabet)





True
isupper() This function returns
True if all the
characters in the
string are in upper case 
str=”I am Learning Python”
print(str.isupper())


str=”I AM LEARNING PYTHON”
print(str.isupper())
False(#contain small case)



True
isspace() This function returns
True if all the
characters in the
string is whitespace. 
str=”I am Learning Python”
print(str.isspace())


str=” “
print(str.isspace())


str = “”
print(str.isspace())
False



True (#contain only space)



False

istitle() This function converts
the given string in
title case(first
alphabet of each
word is in upper case). 
 
str=”i am learning python”
print(str.title())
I Am Learning Python
swapcase() This function converts
the lowercase
characters to upper
case and vice-versa.
str=”I am Learning Python”
print(str.swapcase())
i AM lEARNING pYTHON
Functions of Strings in Python

Practice Questions 

Q1. Write a program to count the frequency of a character in a string.

str=input("Enter any String")
ch=input("Enter the character")
print(str.count(ch))

Q2. Write a program to accept a string and return a string having first letter of each word in capital. 

str=input("Enter any String")
print(str.title())

Q3. Write a program to accept a string and display the following: 

  1. Number of uppercase characters 
  2. Numbers of lowercase characters 
  3. Total number of alphabets 
  4. Number of digits 
str=input("Enter any String")
u=0
L=0
d=0
l = len(str)
for i in range(l):
      if str[i].isupper():
            u = u+1
      if str[i].islower():
            L = L + 1
      if str[i].isdigit():
            d = d+1
print("Total Upper Case Characters are: ", u)
print("Total Lower Case Characters are: ", L)
print("Total Characters are: ", L + u)
print("Total digits are: ", d)

Q4. Write a program to reverse a string.

str=input("Enter any String")
print(str[::-1])

Class 12 Computer Science Sample Paper 2020-2021.

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