str.isdigit()

Added in v3.x · Updated March 13, 2026 · String Methods

stdlib strings character-validation

The isdigit() method returns True if all characters in the string are digits, and False otherwise.

Signature

str.isdigit()

Parameters

None. This method takes no parameters.

Return Value

Returns a boolean value:

True — all characters are digits (0-9)
False — at least one character is not a digit

Examples

>>> "12345".isdigit()
True

>>> "123.45".isdigit()
False

>>> "".isdigit()
False

>>> "-123".isdigit()
False

>>> "\u00b2".isdigit()  # superscript 2
True

Common Use Cases

Input validation:

def get_integer_input(prompt):
    user_input = input(prompt)
    if user_input.isdigit():
        return int(user_input)
    return None

Filtering digit strings:

words = ["apple", "123", "3.14", "42"]
digits_only = [w for w in words if w.isdigit()]
# ["123", "42"]

Notes

Leading signs (+, -) are not considered digits.
Decimal points and commas are not digits.
Unicode superscripts (like \u00b2) are considered digits.
For checking integers including negative numbers, use a custom function or regex.