String in Python has built-in functions for almost every action to be performed on a string. Python String isalnum() function checks for the alphanumeric characters in a string and returns True only if the string consists of alphanumeric characters i.e. either alphabet (a-z, A-Z) or numbers (0-9) or combination of both.
Key Points :
- Return Type: Boolean i.e. True or False
- Parametric Values: No parameters need to be parsed in isalnum() function
- No spaces should be present in the string
- The empty string also returns False
- Not case sensitive i.e. return value does not depend on the case of string
String isalnum() Syntax
str_name.isalnum()
str_name here refers to the input string. And, isalnum() is inbuilt string function in python.
str_name = "Hello123"
print(str_name.isalnum()) # True
String isalnum() Examples
Examples of different cases are given below:
Case 1: String contains only alphabets
str_name = "Hello"
print(str_name.isalnum()) # True
Case 2: String contains only numbers
str_name = "786"
print(str_name.isalnum()) # True
Case 3: String contains spaces in between
str_name = "Welcome user 123"
print(str_name.isalnum()) #False
Case 4: String contains Numbers and Alphabets with different cases
str_name = "w3lC0Me"
print(str_name.isalnum()) # True
Case 5: String contains special characters
str_name = "[email protected]"
print(str_name.isalnum()) # False
Case 6: String is empty or contains whitespaces
str_name = ' '
print(str_name.isalnum()) # False
Program to Print List of All Possible Alphanumeric Characters in Python
The Unicode module can be used to check the alphanumeric character. The program is to print all alphanumeric Unicode characters.
import unicodedata
total_count = 0
for i in range(2 ** 16):
charac = chr(i)
if charac.isalnum():
print(u'{:04x}: {} ({})'.format(i, charac, unicodedata.name(charac, 'UNNAMED')))
total_count = total_count + 1
print("Total Count of Alphanumeric Characters = ",total_count)
Output:

It is just a glance of output as actual output is lengthy. There are 49167 alphanumeric characters in all.
References:
- Python String isalnum()
- Python Built-in String Functions