Python String isalnum()

# string contains either alphabet or number 
name1 = "Python3"

print(name1.isalnum()) #True

# string contains whitespace
name2 = "Python 3"

print(name2.isalnum()) #False

isalnum() Syntax

The syntax of the isalnum() method is:

string.isalnum()

Here, the isalnum() method checks if all the characters of string are alphanumeric or not.

isalnum() Parameters

The isalnum() method doesn't take any parameters.

isalnum() Return Value

The isalnum() method returns:

• True - if all characters in the string are alphanumeric
• False - if at least one character is not alphanumeric

Example 1: Python isalnum()

# contains either numeric or alphabet
string1 = "M234onica"

print(string1.isalnum()) # True 

# contains whitespace
string2 = "M3onica Gell22er"

print(string2.isalnum()) # False

# contains non-alphanumeric character 
string3 = "@Monica!"

print(string3.isalnum()) # False 

Output

True
False
False

In the above example, we have used the isalnum() method with different strings to check if every character in the string is alphanumeric.

Here, string1 contains either alphabet or numerical values so the method returns True.

The method returns False for string2 and string3 because they contain non-alphanumeric characters i.e. whitespace, @, !.

Example 2: isalnum() in if..else Statement

text = "Python#Programming123"

# checks if all the characters are alphanumeric 
if text.isalnum() == True:
   print("All characters of string are alphanumeric.")
else:
    print("All characters are not alphanumeric.")

Output

All characters are not alphanumeric.

Here, we have used the if..else statement to check if all the characters in text are alphanumeric or not.

Since "Python#Programming123" contains # which is neither an alphabet nor a number, text.isalnum() holds False.

So the program executes the else statement.

Recommended readings:

• Python isalpha()
• Python isdigit()