The IP Validator

An easy Python interview practice problem on DataDriven. Write the Python and run it against test cases, with instant feedback.

Domain
Python
Difficulty
easy
Seniority
L3
Asked in
Meta

Problem

Given a string, return True if it is a valid IPv4 address: exactly four decimal octets separated by dots, each in range 0..255, with no leading zeros (except '0' itself).

Real and fake, mixed together.

Example

Input:

ip = "192.168.1.1"

Output:

true

Worked solution and explanation

Why this problem exists in real interviews

This tests string validation with multiple rules, a pattern common in data quality and input sanitization. It probes whether a candidate can enumerate all validation criteria and check them systematically.

Break down the requirements

Step 1: Split by dots and check for exactly 4 parts

A valid IPv4 address has exactly 4 octets separated by dots.

Step 2: Validate each octet

Each must be a numeric string representing an integer between 0 and 255.

Step 3: Check for leading zeros

Octets like '01' or '00' are invalid (except '0' itself).

The solution

Multi-rule IPv4 validation
def is_valid_ipv4(ip: str) -> bool:
    parts = ip.split('.')
    if len(parts) != 4:
        return False
    for part in parts:
        if not part:
            return False
        if not part.isdigit():
            return False
        if len(part) > 1 and part[0] == '0':
            return False
        num = int(part)
        if num < 0 or num > 255:
            return False
    return True

Common follow-up questions