Python Program to accept string ending with alphanumeric character

When it is required to check if a string ends with an alphanumeric character or not, regular expressions can be used. An alphanumeric character is any letter (a-z, A-Z) or digit (0-9). This tutorial demonstrates how to create a function that validates whether a string's last character is alphanumeric.

Using Regular Expressions

The re.search() method can match patterns at the end of a string using the $ anchor ?

import re

regex_expression = '[a-zA-Z0-9]$'

def check_string(my_string):
    if re.search(regex_expression, my_string):
        print("The string ends with alphanumeric character")
    else:
        print("The string does not end with alphanumeric character")

# Test with string ending with special character
my_string_1 = "Python@"
print("The string is:")
print(my_string_1)
check_string(my_string_1)

# Test with string ending with digit
my_string_2 = "Python1245"
print("\nThe string is:")
print(my_string_2)
check_string(my_string_2)

The string is:
Python@
The string does not end with alphanumeric character

The string is:
Python1245
The string ends with alphanumeric character

Using Built-in String Methods

You can also use the isalnum() method to check the last character ?

def check_alphanumeric_ending(text):
    if text and text[-1].isalnum():
        print(f"'{text}' ends with alphanumeric character")
        return True
    else:
        print(f"'{text}' does not end with alphanumeric character")
        return False

# Test cases
test_strings = ["Hello123", "World!", "Test#", "Python3", ""]

for string in test_strings:
    check_alphanumeric_ending(string)
    print()

'Hello123' ends with alphanumeric character

'World!' does not end with alphanumeric character

'Test#' does not end with alphanumeric character

'Python3' ends with alphanumeric character

'' does not end with alphanumeric character

How the Regular Expression Works

• [a-zA-Z0-9] − Character class matching any letter or digit

• $ − Anchor that matches the end of the string

• re.search() − Returns a match object if pattern is found, None otherwise

Comparison of Methods

Conclusion

Use regular expressions with [a-zA-Z0-9]$ pattern for flexible string validation. For simple cases, the isalnum() method on the last character provides a more readable solution.