How do you check if a string is alphanumeric in python?

❮ String Methods


Example

Check if all the characters in the text are alphanumeric:

txt = "Company12"

x = txt.isalnum()

print(x)

Try it Yourself »


Definition and Usage

The isalnum() method returns True if all the characters are alphanumeric, meaning alphabet letter (a-z) and numbers (0-9).

Example of characters that are not alphanumeric: (space)!#%&? etc.


Syntax

Parameter Values

No parameters.


More Examples

Example

Check if all the characters in the text is alphanumeric:

txt = "Company 12"

x = txt.isalnum()

print(x)

Try it Yourself »


❮ String Methods


Python string isalnum() function returns True if it’s made of alphanumeric characters only. A character is alphanumeric if it’s either an alpha or a number. If the string is empty, then isalnum() returns False.

How do you check if a string is alphanumeric in python?

Python string isalnum() example

s = 'HelloWorld2019'
print(s.isalnum())

Output: True

s = 'Hello World 2019'

print(s.isalnum())

Output: False because whitespace is not an alphanumeric character.

s = ''
print(s.isalnum())

Output: False because it’s an empty string.

s='A.B'
print(s.isalnum())

s = '10.50'
print(s.isalnum())

Output:

False
False

The string contains period (.) which is not an alphanumeric character.

s = 'çåøÉ'
print(s.isalnum())

Output: True because all these are Alpha characters. Alphabetic characters are those characters defined in the Unicode character database as “Letter”, i.e., those with general category property being one of “Lm”, “Lt”, “Lu”, “Ll”, or “Lo”.

Printing all Alphanumeric characters in Python

We can use unicode module to check if a character is alphanumeric or not. Here is the program to print all the alphanumeric unicode characters.

import unicodedata

count = 0
for codepoint in range(2 ** 16):
    ch = chr(codepoint)
    if ch.isalnum():
        print(u'{:04x}: {} ({})'.format(codepoint, ch, unicodedata.name(ch, 'UNNAMED')))
        count = count + 1
print(f'Total Number of Alphanumeric Unicode Characters = {count}')

Output:

...
ffd7: ᅲ (HALFWIDTH HANGUL LETTER YU)
ffda: ᅳ (HALFWIDTH HANGUL LETTER EU)
ffdb: ᅴ (HALFWIDTH HANGUL LETTER YI)
ffdc: ᅵ (HALFWIDTH HANGUL LETTER I)
Total Number of Alphanumeric Unicode Characters = 49567

I have provided only partial output because the number of alphanumeric unicode characters is huge.

You can checkout more Python examples from our GitHub Repository.

Reference: Official Documentation

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    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 

    Python String isalnum() Method Example:

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

    Python

    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.

    How do I check if a string contains alphanumeric characters?

    Given string str, the task is to check whether the string is alphanumeric or not by using Regular Expression..
    ^ represents the starting of the string..
    (?= ... .
    (?= ... .
    [A-Za-z0-9] represents whether everything is either alphabetical or digit..
    + represents one or more times..

    How do you find the alphanumeric of a string?

    Java Program to Check String is Alphanumeric or not.
    java. util. regex. *;.
    public static void main(String... s).
    String s1="adA12", s2="jh@l";.
    System. out. println(s1. matches("[a-zA-Z0-9]+"));.
    System. out. println(s2. matches("[a-zA-Z0-9]+"));.

    How do I check if a string contains a non numeric character in Python?

    The isnumeric() method returns True if all the characters are numeric (0-9), otherwise False. Exponents, like ² and ¾ are also considered to be numeric values. "-1" and "1.5" are NOT considered numeric values, because all the characters in the string must be numeric, and the - and the .