Python String isalnum() Method

Python String isalnum() method checks whether all the characters in a given string are either alphabet or numeric (alphanumeric) characters.

Python String isalnum() Method Syntax:

Syntax:  string_name.isalnum() 

Parameter:  isalnum() method takes no parameters 

Return: 

• True: If all the characters are alphanumeric 
• False: If one or more characters are not alphanumeric 

Time Complexity: O(1)

Auxiliary Space: O(1)

Python String isalnum() Method Example:

Python program to demonstrate the use of String isalnum() method

Python

# here a,b and c are characters and 1,2 and 3
# are numbers
string = "abc123"
print(string.isalnum())

Output: 

True

Example 1: More examples on Python String isalnum() Method

Python3

string = "abc 123"
print(string, "is alphanumeric?", string.isalnum())

string = "abc_123"
print(string, "is alphanumeric?", string.isalnum())

string = "000"
print(string, "is alphanumeric?", string.isalnum())

string = "aaaa"
print(string, "is alphanumeric?", string.isalnum())

Output:

abc 123 is alphanumeric? False
abc_123 is alphanumeric? False
000 is alphanumeric? True
aaaa is alphanumeric? True

Example 2: isalnum() in if…else Statement

We can also use Python String isalnum() Method along with if…else statements, to output custom messages

Python3

password = "user123456"

if password.isalnum():
    print("Password is alphanumeric.")
else:
    print("Password is not alphanumeric.")

Output:

Password is alphanumeric.