Check if String is Alphanumeric¶

Check if a string contains alphanumeric characters using the standard library.

12 snippets available in this sub-category.

Simple¶

Check if string is alphanumeric¶

string alphanumeric isalnum validation text

Check if string contains only alphanumeric characters

def is_alphanumeric(text):
    """Check if string contains only alphanumeric characters."""
    return text.isalnum()


text = "Hello123"
result = is_alphanumeric(text)
print(result)  # True

Notes

Uses str.isalnum() method
Checks for letters and digits
Returns boolean
Simple validation

Check if string is alphanumeric with spaces¶

string alphanumeric spaces validation text

Check if string contains only alphanumeric characters and spaces

def is_alphanumeric_with_spaces(text):
    """Check if string contains only alphanumeric characters and spaces."""
    return all(c.isalnum() or c.isspace() for c in text)


text = "Hello 123 World"
result = is_alphanumeric_with_spaces(text)
print(result)  # True

Notes

Uses all() with generator expression
Allows spaces in text
Handles mixed content
Useful for names with numbers

Complex¶

Check if string is alphanumeric with custom characters¶

string alphanumeric custom characters validation text

Check if string contains alphanumeric characters and custom allowed characters

def is_alphanumeric_custom(text, allowed_chars=""):
    """Check if string contains only alphanumeric characters and custom allowed characters."""
    return all(c.isalnum() or c in allowed_chars for c in text)


text = "User123-Name"
result = is_alphanumeric_custom(text, "-_")
print(result)  # True

text2 = "Product@Name"
result2 = is_alphanumeric_custom(text2, "-_")
print(result2)  # False

Notes

Flexible character allowance
Handles usernames with hyphens/underscores
Customizable validation
Useful for identifier validation

Check if string contains at least one letter and one digit¶

string alphanumeric letter digit validation text

Check if string contains at least one letter and one digit

def has_letter_and_digit(text):
    """Check if string contains at least one letter and one digit."""
    has_letter = any(c.isalpha() for c in text)
    has_digit = any(c.isdigit() for c in text)
    return has_letter and has_digit


text = "Hello123"
result = has_letter_and_digit(text)
print(result)  # True

text2 = "Hello"
result2 = has_letter_and_digit(text2)
print(result2)  # False

Notes

Requires both letters and digits
Uses any() with generator expressions
Useful for password validation
Ensures mixed character types

Check if string is alphanumeric with minimum length¶

string alphanumeric length minimum validation text

Check if string is alphanumeric with minimum length requirement

def is_alphanumeric_min_length(text, min_length=1):
    """Check if string is alphanumeric with minimum length requirement."""
    return text.isalnum() and len(text) >= min_length


text = "Hello123"
result = is_alphanumeric_min_length(text, 5)
print(result)  # True

text2 = "Hi1"
result2 = is_alphanumeric_min_length(text2, 5)
print(result2)  # False

Notes

Combines alphanumeric check with length
Configurable minimum length
Useful for form validation
Prevents short inputs

Check if string is alphanumeric with maximum length¶

string alphanumeric length maximum validation text

Check if string is alphanumeric with maximum length requirement

def is_alphanumeric_max_length(text, max_length):
    """Check if string is alphanumeric with maximum length requirement."""
    return text.isalnum() and len(text) <= max_length


text = "Hello123"
result = is_alphanumeric_max_length(text, 10)
print(result)  # True

text2 = "VeryLongAlphanumericString123"
result2 = is_alphanumeric_max_length(text2, 10)
print(result2)  # False

Notes

Combines alphanumeric check with length
Configurable maximum length
Useful for form validation
Prevents overly long inputs

Check if string is alphanumeric with length range¶

string alphanumeric length range validation text

Check if string is alphanumeric within specified length range

def is_alphanumeric_length_range(text, min_length=1, max_length=None):
    """Check if string is alphanumeric within length range."""
    if not text.isalnum():
        return False

    length = len(text)
    if length < min_length:
        return False

    if max_length is not None and length > max_length:
        return False

    return True


text = "Hello123"
result = is_alphanumeric_length_range(text, 5, 15)
print(result)  # True

text2 = "Hi1"
result2 = is_alphanumeric_length_range(text2, 5, 15)
print(result2)  # False

Notes

Flexible length range checking
Optional maximum length
Comprehensive validation
Useful for form validation

Check if string starts with alphanumeric¶

string alphanumeric start validation text

Check if string starts with an alphanumeric character

def starts_with_alphanumeric(text):
    """Check if string starts with an alphanumeric character."""
    return bool(text and text[0].isalnum())


text = "Hello123"
result = starts_with_alphanumeric(text)
print(result)  # True

text2 = "!Hello123"
result2 = starts_with_alphanumeric(text2)
print(result2)  # False

Notes

Checks first character only
Handles empty strings
Simple position check
Useful for validation

Check if string ends with alphanumeric¶

string alphanumeric end validation text

Check if string ends with an alphanumeric character

def ends_with_alphanumeric(text):
    """Check if string ends with an alphanumeric character."""
    return bool(text and text[-1].isalnum())


text = "Hello123"
result = ends_with_alphanumeric(text)
print(result)  # True

text2 = "Hello123!"
result2 = ends_with_alphanumeric(text2)
print(result2)  # False

Notes

Checks last character only
Handles empty strings
Simple position check
Useful for validation

Check if string contains specific alphanumeric pattern¶

string alphanumeric pattern regex validation text

Check if string matches specific alphanumeric pattern

def matches_alphanumeric_pattern(text, pattern):
    """Check if string matches alphanumeric pattern."""
    import re

    return bool(re.match(pattern, text))


text = "Hello123"
result = matches_alphanumeric_pattern(text, r"^[A-Za-z]+\d+$")
print(result)  # True

text2 = "123Hello"
result2 = matches_alphanumeric_pattern(text2, r"^[A-Za-z]+\d+$")
print(result2)  # False

Notes

Uses regex pattern matching
Flexible pattern definition
Powerful validation
Useful for complex rules

Check if string is valid identifier¶

string alphanumeric identifier validation text

Check if string is a valid Python identifier

def is_valid_identifier(text):
    """Check if string is a valid Python identifier."""
    return text.isidentifier()


text = "hello_123"
result = is_valid_identifier(text)
print(result)  # True

text2 = "123hello"
result2 = is_valid_identifier(text2)
print(result2)  # False

Notes

Uses str.isidentifier() method
Follows Python naming rules
Cannot start with digit
Useful for variable names

Check if string is valid username¶

string alphanumeric username validation text

Check if string is a valid username

def is_valid_username(text, min_length=3, max_length=20):
    """Check if string is a valid username."""
    if not text:
        return False

    # Check length
    if len(text) < min_length or len(text) > max_length:
        return False

    # Check if starts with letter
    if not text[0].isalpha():
        return False

    # Check if contains only alphanumeric and underscore
    return all(c.isalnum() or c == "_" for c in text)


text = "user_123"
result = is_valid_username(text)
print(result)  # True

text2 = "123user"
result2 = is_valid_username(text2)
print(result2)  # False

Notes

Custom username validation rules
Starts with letter requirement
Allows underscores
Configurable length limits

🔗 Cross-References¶

Reference: See 📂 Is Alpha
Reference: See 📂 Is Numeric

🏷️ Tags¶

string, alphanumeric, isalnum, validation, text

📝 Notes¶

Use str.isalnum() to check for alphanumeric strings
Returns True if all characters are letters or digits
Useful for input validation and parsing