Improve type hints (python-pillow#8883)

Author: hugovk

Tests/test_file_avif.py

@@ -254,7 +254,9 @@ def test_load_transparent_rgb(self) -> None:
             assert_image(im, "RGBA", (64, 64))
 
             # image has 876 transparent pixels
-            assert im.getchannel("A").getcolors()[0] == (876, 0)
+            colors = im.getchannel("A").getcolors()
+            assert colors is not None
+            assert colors[0] == (876, 0)
 
     def test_save_transparent(self, tmp_path: Path) -> None:
         im = Image.new("RGBA", (10, 10), (0, 0, 0, 0))

Tests/test_file_gif.py

@@ -540,7 +540,9 @@ def test_dispose_background_transparency() -> None:
         img.seek(2)
         px = img.load()
         assert px is not None
-        assert px[35, 30][3] == 0
+        value = px[35, 30]
+        assert isinstance(value, tuple)
+        assert value[3] == 0
 
 
 @pytest.mark.parametrize(
@@ -1422,7 +1424,9 @@ def test_getdata(monkeypatch: pytest.MonkeyPatch) -> None:
 def test_lzw_bits() -> None:
     # see https://github.com/python-pillow/Pillow/issues/2811
     with Image.open("Tests/images/issue_2811.gif") as im:
-        assert im.tile[0][3][0] == 11  # LZW bits
+        args = im.tile[0][3]
+        assert isinstance(args, tuple)
+        assert args[0] == 11  # LZW bits
         # codec error prepatch
         im.load()
 
@@ -1477,7 +1481,11 @@ def test_saving_rgba(tmp_path: Path) -> None:
 
     with Image.open(out) as reloaded:
         reloaded_rgba = reloaded.convert("RGBA")
-        assert reloaded_rgba.load()[0, 0][3] == 0
+        px = reloaded_rgba.load()
+        assert px is not None
+        value = px[0, 0]
+        assert isinstance(value, tuple)
+        assert value[3] == 0
 
 
 @pytest.mark.parametrize("params", ({}, {"disposal": 2, "optimize": False}))

Tests/test_file_jpeg.py

@@ -130,33 +130,27 @@ def test_comment_write(self) -> None:
     def test_cmyk(self) -> None:
         # Test CMYK handling.  Thanks to Tim and Charlie for test data,
         # Michael for getting me to look one more time.
-        f = "Tests/images/pil_sample_cmyk.jpg"
-        with Image.open(f) as im:
-            # the source image has red pixels in the upper left corner.
-            c, m, y, k = (x / 255.0 for x in im.getpixel((0, 0)))
-            assert c == 0.0
-            assert m > 0.8
-            assert y > 0.8
-            assert k == 0.0
-            # the opposite corner is black
-            c, m, y, k = (
-                x / 255.0 for x in im.getpixel((im.size[0] - 1, im.size[1] - 1))
-            )
-            assert k > 0.9
-            # roundtrip, and check again
-            im = self.roundtrip(im)
+        def check(im: ImageFile.ImageFile) -> None:
             cmyk = im.getpixel((0, 0))
             assert isinstance(cmyk, tuple)
             c, m, y, k = (x / 255.0 for x in cmyk)
             assert c == 0.0
             assert m > 0.8
             assert y > 0.8
             assert k == 0.0
+            # the opposite corner is black
             cmyk = im.getpixel((im.size[0] - 1, im.size[1] - 1))
             assert isinstance(cmyk, tuple)
             k = cmyk[3] / 255.0
             assert k > 0.9
 
+        with Image.open("Tests/images/pil_sample_cmyk.jpg") as im:
+            # the source image has red pixels in the upper left corner.
+            check(im)
+
+            # roundtrip, and check again
+            check(self.roundtrip(im))
+
     def test_rgb(self) -> None:
         def getchannels(im: JpegImagePlugin.JpegImageFile) -> tuple[int, ...]:
             return tuple(v[0] for v in im.layer)

Tests/test_file_mpo.py

@@ -156,6 +156,7 @@ def test_reload_exif_after_seek() -> None:
 def test_mp(test_file: str) -> None:
     with Image.open(test_file) as im:
         mpinfo = im._getmp()
+        assert mpinfo is not None
         assert mpinfo[45056] == b"0100"
         assert mpinfo[45057] == 2
 
@@ -165,6 +166,7 @@ def test_mp_offset() -> None:
     # in APP2 data, in contrast to normal 8
     with Image.open("Tests/images/sugarshack_ifd_offset.mpo") as im:
         mpinfo = im._getmp()
+        assert mpinfo is not None
         assert mpinfo[45056] == b"0100"
         assert mpinfo[45057] == 2
 
@@ -181,6 +183,7 @@ def test_mp_no_data() -> None:
 def test_mp_attribute(test_file: str) -> None:
     with Image.open(test_file) as im:
         mpinfo = im._getmp()
+    assert mpinfo is not None
     for frame_number, mpentry in enumerate(mpinfo[0xB002]):
         mpattr = mpentry["Attribute"]
         if frame_number:

Tests/test_file_tga.py

@@ -220,12 +220,16 @@ def test_horizontal_orientations() -> None:
     with Image.open("Tests/images/rgb32rle_top_right.tga") as im:
         px = im.load()
         assert px is not None
-        assert px[90, 90][:3] == (0, 0, 0)
+        value = px[90, 90]
+        assert isinstance(value, tuple)
+        assert value[:3] == (0, 0, 0)
 
     with Image.open("Tests/images/rgb32rle_bottom_right.tga") as im:
         px = im.load()
         assert px is not None
-        assert px[90, 90][:3] == (0, 255, 0)
+        value = px[90, 90]
+        assert isinstance(value, tuple)
+        assert value[:3] == (0, 255, 0)
 
 
 def test_save_rle(tmp_path: Path) -> None:

Tests/test_file_webp.py

@@ -219,6 +219,7 @@ def test_background_from_gif(self, tmp_path: Path) -> None:
         # Save P mode GIF with background
         with Image.open("Tests/images/chi.gif") as im:
             original_value = im.convert("RGB").getpixel((1, 1))
+            assert isinstance(original_value, tuple)
 
             # Save as WEBP
             im.save(out_webp, save_all=True)
@@ -230,6 +231,7 @@ def test_background_from_gif(self, tmp_path: Path) -> None:
 
         with Image.open(out_gif) as reread:
             reread_value = reread.convert("RGB").getpixel((1, 1))
+        assert isinstance(reread_value, tuple)
         difference = sum(abs(original_value[i] - reread_value[i]) for i in range(3))
         assert difference < 5