Question

How to count the number of digits in an integer with Python

Answer 1

def count_digits_string(value: int) -> int:
    """
    Counts digits by converting the number to a string.
    This approach is clear, safe, and widely used in everyday Python code.
    """
    text = str(value)

    # If negative, ignore the leading '-'
    if text.startswith("-"):
        return len(text) - 1

    return len(text)


number = -12345
digits = count_digits_string(number)

print("Number:", number)
print("Digit count (String method):", digits)


"""
run:

Number: -12345
Digit count (String method): 5

"""

 

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Answer 2

import math

def count_digits_log10(value: int) -> int:
    """
    Counts digits using log10.
    Uses the formula: floor(log10(n)) + 1
    Zero is handled separately because log10(0) is undefined.
    """
    num = abs(value)

    if num == 0:
        return 1

    return int(math.floor(math.log10(num))) + 1


number = 987654321
digits = count_digits_log10(number)

print("Number:", number)
print("Digit count (log10 method):", digits)


"""
run:

Number: 987654321
Digit count (log10 method): 9

"""

 

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