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Asked: 2026-05-11T05:20:07+00:00

In this other question , the votes clearly show that the os.path.splitext function is

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In this other question, the votes clearly show that the os.path.splitext function is preferred over the simple .split('.')[-1] string manipulation. Does anyone have a moment to explain exactly why that is? Is it faster, or more accurate, or what? I’m willing to accept that there’s something better about it, but I can’t immediately see what it might be. Might importing a whole module to do this be overkill, at least in simple cases?

EDIT: The OS specificity is a big win that’s not immediately obvious; but even I should’ve seen the ‘what if there isn’t a dot’ case! And thanks to everybody for the general comments on library usage.

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  1. Well, there are separate implementations for separate operating systems. This means that if the logic to extract the extension of a file differs on Mac from that on Linux, this distinction will be handled by those things. I don’t know of any such distinction so there might be none.

    Edit: @Brian comments that an example like /directory.ext/file would of course not work with a simple .split('.') call, and you would have to know both that directories can use extensions, as well as the fact that on some operating systems, forward slash is a valid directory separator.

    This just emphasizes the use a library routine unless you have a good reason not to part of my answer.

    Thanks @Brian.

    Additionally, where a file doesn’t have an extension, you would have to build in logic to handle that case. And what if the thing you try to split is a directory name ending with a backslash? No filename nor an extension.

    The rule should be that unless you have a specific reason not to use a library function that does what you want, use it. This will avoid you having to maintain and bugfix code others have perfectly good solutions to.

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