Python - String isalnum() Method

The isalnum() string method returns True only if all the characters in the invoked string are -

Alphabets, either lower case alphabets i.e. a-z or upper case alphabets from A-Z, or
Digits i.e. 0-9

In all other cases, the isalnum(), returns False.

Note : None of the string methods change the original string and only return a new string which reflects the change performed by the string method, hence the returned string must be stored or used(if needed to reflect the result), otherwise it is lost.

Signature of isalnum()

The isalnum() method has no parameters, so we don't have to worry about passing it some value.

# Signature of isalnum() method 
isalnum()

Calling isalnum() method on a string object.

isalnum()

# Python - An example of isalnum() method


# Creating the first string
s3 = ('QuackQuack')

# Printing the third string
print('The third string : ', s3)

# Calling  the isalnum() method on third string object 
print('isalnum() method on third string : ', s3.isalnum())


# Creating the second string
s2 = ('Woof Woof')

# Printing the second string
print('The second string : ', s2)

# Calling  the isalnum() method on second string object 
print('isalnum() method on second string : ', s2.isalnum())



# Creating the third string
s2 = ('321Go')

# Printing the third string
print('The third string : ', s2)

# Calling  the isalnum() method on third string object 
print('isalnum() method on third string : ', s2.isalnum())

Output

The third string :  QuackQuack
isalnum() method on third string :  True
The second string :  Woof Woof
isalnum() method on second string :  False
The third string :  321Go
isalnum() method on third string :  True

Program Analysis

Calling the isalnum() on the first string of all characters, returns True.
Calling the isalnum() on the second string of all characters(except an empty space), returns False, because an empty space in a string is not an alphabet.
Calling the isalnum() on the third string of all characters and digits, returns True.

Another example of isalnum() method

The isalnum() method returns a bool False on a string made up of any special character or symbols, except lower case or upper case alphabets or digits. Let us see a few more examples of calling the isalnum() method on all different forms of strings.

# Python - Method isalnum() Example



# Creating the first string
s1 = ('Robot2.0')

# Printing the first string
print('The first string : ', s1)

# Calling  the isalnum() method on first string object 
print('isalnum() method on first string : ', s1.isalnum())



# Creating the second string
s2 = ('The_Blue_Umbrella')

# Printing the second string
print('The second string : ', s2)

# Calling  the isalnum() method on second string object 
print('isalnum() method on second string : ', s2.isalnum())




# Creating the third string
s4 = ('Salut!')

# Printing the third string
print('The third string : ', s4)

# Calling  the isalnum() method on third string object 
print('isalnum() method on third string : ', s4.isalnum())

Output

The first string :  Robot2.0
isalnum() method on first string :  False
The second string :  The_Blue_Umbrella
isalnum() method on second string :  False
The third string :  Salut!
isalnum() method on third string :  False

Program Analysis

Calling the isalnum() on the first string of all characters and digits(except a dot), returns False.
Calling the isalnum() on the second string of all characters(except underscores), returns False.
Calling the isalnum() on the third string of all characters(except an !), returns False.