Python – recursive function returns None

Question

I’m trying to sanitise the URL, and extract only Id’s from it (by skipping the URL part). By doing some debugging, I can see the value im looking for is printing, however, not returning (or returns None)

This is the code:

def _sanitize_urls(urls=None):
    redact_list = [
        ("abcd.google.com", 3),
        ("xyz.yahoo.com", 4),
    ]
    urls_sanitized = []
    redact_found = [redact for redact in redact_list if redact[0] in urls]
    if redact_found:
        urls = urls.split(" ")
        print(urls)
        urls_sanitized = [
            words.split("/")[redact_found[0][1]] if redact_found[0][0] in words else words for words in urls
        ]
        print(urls_sanitized)
        urls_sanitized = " ".join(urls_sanitized)
        print(urls_sanitized)
        redact_found = [redact for redact in redact_list if redact[0] in urls_sanitized]
        print(redact_found)
        if not redact_found:
            print(urls_sanitized)
            return urls_sanitized
        else:
            _sanitize_urls(urls_sanitized)


def main():
    urls = "https://abcd.google.com/ID-XXXX and https://xyz.yahoo.com/Id/ID-XXXX"
    redact_exists = _sanitize_urls(urls)
    print(redact_exists)


if __name__ == "__main__":
    main()

Output Im expecting is => “ID-XXXX and ID-XXXX”. Output I’m getting right now is None.

With some debugging on my side =>

['https://abcd.google.com/ID-XXXX', 'and', 'https://xyz.yahoo.com/Id/ID-XXXX']
['ID-XXXX', 'and', 'https://xyz.yahoo.com/Id/ID-XXXX']
ID-XXXX and https://xyz.yahoo.com/Id/ID-XXXX
[('xyz.yahoo.com', 4)]
['ID-XXXX', 'and', 'https://xyz.yahoo.com/Id/ID-XXXX']
['ID-XXXX', 'and', 'ID-XXXX']
ID-XXXX and ID-XXXX
[]
ID-XXXX and ID-XXXX
None

As you can see, print, prints the correct value, till the last moment, however its not returning to main function, rather returning None. Any ideas?

Asked By: Danny

||

Source

Answer 1

In the last line of your _sanitize_urls function, you have

 _sanitize_urls(urls_sanitized)

There’s no more code to your function after this. In Python, if a function runs out of code without an explicit return statement, None will be returned automatically.

Answered By: Daniel Walker

Python – recursive function returns None

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