Validate a URL in Python (regex and urllib.parse)

This program checks whether a string looks like a web address: http:// or https://, then a domain name with at least one dot, then an optional port and path.

The program

python

import re

URL_PATTERN = re.compile(r"https?://([A-Za-z0-9-]+\.)+[A-Za-z]{2,}(:\d{1,5})?(/\S*)?")


def is_valid_url(url):
    return URL_PATTERN.fullmatch(url) is not None


tests = [
    "https://www.example.com",
    "http://example.org/docs/page?id=7#top",
    "https://example.com:8080/api",
    "www.example.com",
    "ftp://example.com",
    "https://exa mple.com",
    "https://localhost:8000",
]
for url in tests:
    print(f"{url:40} {is_valid_url(url)}")

output

https://www.example.com                  True
http://example.org/docs/page?id=7#top    True
https://example.com:8080/api             True
www.example.com                          False
ftp://example.com                        False
https://exa mple.com                     False
https://localhost:8000                   False

How it works

https?:// matches http:// or https://. The ? makes the s optional.
([A-Za-z0-9-]+\.)+[A-Za-z]{2,} is the domain: one or more labels that end with a dot (www., example.), then an ending of two or more letters (com).
(:\d{1,5})? is an optional port, such as :8080.
(/\S*)? is an optional path. \S means any character that is not a space, so the path can contain ?, = and #.
www.example.com fails because it has no http:// or https://. https://localhost:8000 fails because localhost has no dot. If you need to accept local addresses, change the domain part of the pattern.

Another way: urllib.parse

The standard library can split a URL into its parts. That is easier to read than a long regex, and you can then check each part:

python

from urllib.parse import urlparse

parts = urlparse("https://example.com:8080/docs/page?id=7#top")
print("scheme:  ", parts.scheme)
print("host:    ", parts.hostname)
print("port:    ", parts.port)
print("path:    ", parts.path)
print("query:   ", parts.query)
print("fragment:", parts.fragment)


def is_web_url(url):
    parts = urlparse(url)
    return parts.scheme in ("http", "https") and bool(parts.hostname) and " " not in url


print(is_web_url("https://www.example.com"), is_web_url("www.example.com"))

output

scheme:   https
host:     example.com
port:     8080
path:     /docs/page
query:    id=7
fragment: top
True False

urlparse() does not raise an error for a bad URL. It splits whatever you give it, so you still have to check that the parts you need are there.

URL validation in Python

The program

How it works

Another way: urllib.parse