Python String isalnum() Method

Last Updated : 21 Apr, 2025

The isalnum() method is a string function in Python that checks if all characters in the given string are alphanumeric. If every character is either a letter or a number, isalnum() returns True. Otherwise, it returns False.

For Example:

Python

s = "Python123" res = s.isalnum() print(res)

Output

True

Explanation: In this example, s contains only letters and numbers, so isalnum() returns True.

Syntax

s.isalnum()

Parameters:

This method does not accept any parameters.

Return Type:

Returns True if all characters in the string are alphanumeric.
Returns False if there are any non-alphanumeric characters.

Examples of isalnum() Method

Example 1: Empty String

An empty string will return False since there are no alphanumeric characters.

Python

s = "" res = s.isalnum() print(res)

Output

False

Example 2: String with Only Digits

The method will also return True for a string with only numeric characters.

Python

s = "123456" res = s.isalnum() print(res)

Output

True

Example 3: String with Only Letters

Similarly, a string containing only letters will return True.

Python

s = "Python" res = s.isalnum() print(res)

Output

True

Example 4: String with Non-Alphanumeric Characters

If the string contains a space and an exclamation mark, so isalnum() returns False.

Python

s = "Python 123!" res = s.isalnum() print(res)

Output

False

Explanation: in this code, isalnum() returns False because the string s contains space " " and exclamation mark (!) which are neither numbers nor alphabets.

Python String casefold() Method

S

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