Context

mimetypes.guess_type() is intended for URLs, while mimetypes.guess_file_type() was introduced in Python 3.13 as the preferred API for file paths.

The implementation still accepts file paths without warning, despite the existing # TODO: Deprecate accepting file paths (in particular path-like objects) comment in Lib/mimetypes.py. This PR implements that TODO by deprecating file path inputs to guess_type() and directing users to guess_file_type() instead.

Changes Made

• Implementation: Modified mimetypes.MimeTypes.guess_type() to emit a DeprecationWarning (stacklevel=2) when called with a file path instead of a URL.

• Coverage: The warning triggers for plain strings that do not contain a valid URL scheme, as well as for bytes and os.PathLike objects. Valid URLs such as http://, ftp://, and data: continue to behave as before.

• Testing: Added GuessTypeDeprecationTestCase to Lib/test/test_mimetypes.py covering path and URL inputs to verify warning behavior and prevent regressions.

• Documentation:

  • Updated Doc/library/mimetypes.rst to document the runtime deprecation.
  • Added entries to Doc/whatsnew/3.16.rst and Doc/deprecations/pending-removal-in-future.rst.

• NEWS: Added the required NEWS entry using blurb.

Rationale

This change aligns the runtime behavior with the documented distinction between URL handling (guess_type()) and file-path handling (guess_file_type()), while implementing the existing deprecation TODO in the source code.

Linked Issue

Fixes #151575

Code of Conduct and CLA

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• Issue: Deprecate passing file paths instead of URLs to mimetypes.guess_type() #151575