Speed up mimetypes.guess_type() for plain file paths

[gaborbernat]

mimetypes.guess_type() accepts either a URL or a filesystem path, so it parses its argument as a URL with urllib.parse.urlparse() before looking at the extension. The common argument is a plain file path, which has no URL scheme to find, so the parse and the urllib.parse import it pulls in are spent on nothing.

Guessing content types from file names is everywhere: static-file servers, upload handlers, archive and build tools deciding how to treat each file as they walk a tree of thousands.

Guessing types for 15 real file names sampled from the top-1000 corpus takes 23.4 µs today and 11.0 µs when a plain path skips the URL parse and goes straight to extension lookup, 112% faster. Real URLs still take the full parsing path, and results are unchanged for both.

Linked PRs

• gh-150821: Skip URL parsing in mimetypes.guess_type() for file paths #150828

[serhiy-storchaka]

Using guess_type() for file paths is deprecated. Use guess_file_type() instead.