Day 74: Python Validate IPv4 Address – String Parsing Mastery for Perfect IP Check (No Libraries Needed)

Source: Dev.to

Key Takeaways from Day 74: IPv4 Validation Function

Function Design: Split and Basic Count Check

def is_valid_ipv4(ip: str) -> bool:
    """Return True if the given string is a valid IPv4 address."""
    parts = ip.split(".")  # split address into parts

    if len(parts) != 4:
        return False  # IPv4 must have exactly 4 parts

Loop Processing: Per‑Part Rules Validation

    for part in parts:
        if part == "":
            return False               # empty segment is invalid

        if not part.isdigit():
            return False               # must contain digits only

        if len(part) > 1 and part[0] == "0":
            return False               # no leading zeros allowed

        value = int(part)
        if value  255:
            return False               # each part must be in range 0–255

    return True

Main Interactive: Input and Bool Print

ip = input("Enter an IPv4 address: ").strip()
result = is_valid_ipv4(ip)

print(f"Is valid IPv4: {result}")

Summary and Reflections

This IPv4 validator uses split and layered rules for accurate checks.

• Parse early – splitting filters the structure quickly.
• Rule layers – empty segment, digit‑only, leading zero, and range checks are applied sequentially.
• No external libraries – manual validation deepens understanding of string parsing and numeric constraints.

Potential extensions include subnet validation or IPv6 support.

Next Steps and Resources

• Source Code for Challenge #74: scripts/validate_ipv4.py
• Main Repository: 80-days-of-challenges
• Daily Updates: Twitter/X (@Shahrouzlogs)