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

filetype/filetype.py

@@ -2,6 +2,8 @@
 
 from __future__ import absolute_import
 
+from os import PathLike
+
 from .match import match
 from .types import TYPES, Type
 
@@ -96,3 +98,34 @@ def add_type(instance):
         raise TypeError('instance must inherit from filetype.types.Type')
 
     types.insert(0, instance)
+
+
+# Convert filetype extensions to imghdr extensions
+imghdr_exts = {"jpg": "jpeg", "tif": "tiff"}
+
+
+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:
+    ```python
+    # Replace...
+    from imghdr import what
+    # with...
+    from filetype import what
+    # ---
+    # Or replace...
+    import imghdr
+    ext = imghdr.what(...)
+    # with...
+    import filetype
+    ext = filetype.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
+    """
+    image_type = guess(h) if h else guess(file)
+    ext = str(image_type) if image_type else None
+    return imghdr_exts.get(ext, ext)

filetype/types/base.py

@@ -11,6 +11,12 @@ def __init__(self, mime, extension):
         self.__mime = mime
         self.__extension = extension
 
+    def __str__(self):
+        return f"{self.extension}"
+
+    def __repr__(self):
+        return f"{self.__class__.__name__}({self.__mime}, {self.__extension})"
+
     @property
     def mime(self):
         return self.__mime

tests/test_what.py

@@ -0,0 +1,130 @@
+from __future__ import annotations
+
+from pathlib import Path
+from sys import version_info
+from warnings import filterwarnings
+
+import pytest
+
+from filetype.filetype import what
+
+filterwarnings("ignore", message="'imghdr' is deprecated")
+try:  # imghdr was removed from the standard library in Python 3.13
+    from imghdr import what as imghdr_what
+except ModuleNotFoundError:
+    imghdr_what = None
+
+# file_tests = sorted(test_func.__name__[5:] for test_func in imghdr.tests)
+# file_tests = "bmp exr gif jpg pbm pgm png ppm ras rgb tif webp xbm".split()
+file_tests = "gif jpg png tif".split()  # TODO: (cclauss) Add the remaining files
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize("file", file_tests)
+def test_what_from_file(file, h=None):
+    """Run each test with a path string and a pathlib.Path."""
+    file = f"tests/fixtures/sample.{file}"
+    assert what(file, h) == imghdr_what(file, h)
+    file = Path(file).resolve()
+    assert what(file, h) == imghdr_what(file, h)
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+def ztest_what_from_file_none(file="tests/fixtures/sample_skippable.zst", h=None):
+    assert what(file, h) == imghdr_what(file, h) is None
+    file = Path(file).resolve()
+    assert what(file, h) == imghdr_what(file, h) is None
+
+
+string_tests = [
+    ("bmp", "424d"),
+    ("bmp", "424d787878785c3030305c303030"),
+    ("bmp", b"BM"),
+    ("gif", "474946383761"),
+    ("gif", b"GIF87a"),
+    ("gif", b"GIF89a"),
+    ("png", "89504e470d0a1a0a"),
+    ("png", b"\211PNG\r\n\032\n"),
+    (None, "decafbad"),
+    (None, b"decafbad"),
+]
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize("expected, h", string_tests)
+def test_what_from_string(expected, h):
+    if isinstance(h, str):  # In imgdir.what() h must be bytes, not str.
+        h = bytes.fromhex(h)
+    assert imghdr_what(None, h) == what(None, h) == expected
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize(
+    "expected, h",
+    [
+        ("jpeg", "ffd8ffdb"),
+        ("jpeg", b"\xff\xd8\xff\xdb"),
+    ],
+)
+def test_what_from_string_py311(expected, h):
+    """
+    These tests fail with imghdr on Python < 3.11.
+    TODO: (cclauss) Document these imghdr fails on Python < 3.11
+    """
+    if isinstance(h, str):  # In imgdir.what() h must be bytes, not str.
+        h = bytes.fromhex(h)
+    assert what(None, h) == expected
+    if version_info < (3, 11):  # TODO: Document these imghdr fails
+        expected = None
+    assert imghdr_what(None, h) == expected
+
+
+@pytest.mark.skipif(imghdr_what is None, reason="imghdr was removed from the standard library in Python 3.13")
+@pytest.mark.parametrize(
+    "expected, h",
+    [
+        # ("exr", "762f3101"),
+        ("exr", b"\x76\x2f\x31\x01"),
+        ("jpeg", b"______JFIF"),
+        ("jpeg", b"______Exif"),
+        ("pbm", b"P1 "),
+        ("pbm", b"P1\n"),
+        ("pbm", b"P1\r"),
+        ("pbm", b"P1\t"),
+        ("pbm", b"P4 "),
+        ("pbm", b"P4\n"),
+        ("pbm", b"P4\r"),
+        ("pbm", b"P4\t"),
+        ("pgm", b"P2 "),
+        ("pgm", b"P2\n"),
+        ("pgm", b"P2\r"),
+        ("pgm", b"P2\t"),
+        ("pgm", b"P5 "),
+        ("pgm", b"P5\n"),
+        ("pgm", b"P5\r"),
+        ("pgm", b"P5\t"),
+        ("ppm", b"P3 "),
+        ("ppm", b"P3\n"),
+        ("ppm", b"P3\r"),
+        ("ppm", b"P3\t"),
+        ("ppm", b"P6 "),
+        ("ppm", b"P6\n"),
+        ("ppm", b"P6\r"),
+        ("ppm", b"P6\t"),
+        ("rast", b"\x59\xA6\x6A\x95"),
+        ("rgb", b"\001\332"),
+        ("tiff", b"II"),
+        ("tiff", b"MM"),
+        ("webp", b"RIFF____WEBP"),
+        ("xbm", b"#define "),
+    ],
+)
+def test_what_from_string_todo(expected, h):
+    """
+    These tests pass with imghdr but fail with filetype.
+    TODO: (cclauss) Fix these filetype fails
+    """
+    if isinstance(h, str):  # In imgdir.what() h must be bytes, not str.
+        h = bytes.fromhex(h)
+    assert imghdr_what(None, h) == expected
+    assert what(None, h) is None

tox.ini

@@ -29,7 +29,7 @@ deps =
 commands = flake8 {toxinidir} --extend-exclude tests,docs,build,dist,venv,.venv --extend-ignore=E501
 
 [testenv:doc]
-basepython = python3
+basepython = python3.10  # pdoc3/pdoc#438
 deps =
      pdoc3
 commands = pdoc --html --force --output-dir docs filetype