pythonOtherMedium

Removing https:// eats the start of shop.com

Time: 0:00

BugFind the bug and fix the code

What it should do

domain_of(url) removes "https://" from the front of a web address. Example: domain_of("https://shop.com") → "shop.com".

What happens instead

domain_of("https://shop.com") returns "op.com". domain_of("https://example.org") works.

def domain_of(url):
    return url.strip("https://")

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

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This bug belongs to the mutation and copying bugs pattern

Assignment does not copy, a shallow copy still shares its contents, and mutating methods return None.

Learn the mutation and copying bugs pattern Step through your own code

Spoiler: why this bug happens(try it first; the hints get warmer one at a time)

What went wrong: strip("https://") removes any of those characters from the ends. After the prefix, it keeps going and removes the s and h of "shop".

The fix: return url.removeprefix("https://")

Remember: strip() removes characters, not words. Use removeprefix() or removesuffix().

The pattern behind it: mutation and copying bugs.

More mutation and copying bugs to practise

Seen this error in your own code?

str.strip() removes more than you asked

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