Python String isalnum() Method

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:

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

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.

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

False

Example 2: String with Only Digits

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

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

True

Example 3: String with Only Letters

Similarly, a string containing only letters will return True.

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

True

Example 4: String with Non-Alphanumeric Characters

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

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

False

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