For Python 3.13: A drop-in replacement for `imghdr.what()`

[cclauss]

The Python 3.13 release notes mention python-magic as one of the alternatives for imghdr which was removed from the Standard Library.

Given the discussion in #317, it might be quite helpful to have a drop-in replacement for imghdr.what(). It would provide a smooth transition to Py3.13 if developers could confidently replace all instances of imghdr.what() with magic.what() -- same args, same results.

• 317

  ---

Current pytest results: 45 passed in 0.05s

• test_what_from_file is 2 tests
• ztest_what_from_file_none is 0 test -- disabled with the leading z
• test_what_from_string is 10 tests
• test_what_from_string_py311 is 2 tests
  • Fail on imghdr only on Python < 3.11
• test_what_from_string_todo is 31 tests -- Lots of work to do!
  • Fail on magic

def what(file: PathLike | str | None, h: bytes | None) -> str:
    """A drop-in replacement for `imghdr.what()` which was removed from the standard
    library in Python 3.13."""

Usage:

# Replace...
from imghdr import what
# with...
from magic import what

# Or replace...
import imghdr
ext = imghdr.what(...)
# with...
import magic
ext = magic.what(...)

imghdr documentation: https://docs.python.org/3.12/library/imghdr.html imghdr source code: https://github.com/python/cpython/blob/3.12/Lib/imghdr.py

[cclauss]

Closing in favor of puremagic.what() because it has better recognition of image file formats.