Replace slice and comparison with startswith/endswith

Tests/test_file_mpo.py

@@ -77,8 +77,8 @@ def test_app(test_file: str) -> None:
     with Image.open(test_file) as im:
         assert im.applist[0][0] == "APP1"
         assert im.applist[1][0] == "APP2"
-        assert (
-            im.applist[1][1][:16] == b"MPF\x00MM\x00*\x00\x00\x00\x08\x00\x03\xb0\x00"
+        assert im.applist[1][1].startswith(
+            b"MPF\x00MM\x00*\x00\x00\x00\x08\x00\x03\xb0\x00"
         )
         assert len(im.applist) == 2
 

Tests/test_file_webp_metadata.py

@@ -40,7 +40,7 @@ def test_read_exif_metadata() -> None:
 def test_read_exif_metadata_without_prefix() -> None:
     with Image.open("Tests/images/flower2.webp") as im:
         # Assert prefix is not present
-        assert im.info["exif"][:6] != b"Exif\x00\x00"
+        assert not im.info["exif"].startswith(b"Exif\x00\x00")
 
         exif = im.getexif()
         assert exif[305] == "Adobe Photoshop CS6 (Macintosh)"

Tests/test_image.py

@@ -74,12 +74,12 @@ def test_exception_inheritance(self) -> None:
 
     def test_sanity(self) -> None:
         im = Image.new("L", (100, 100))
-        assert repr(im)[:45] == "<PIL.Image.Image image mode=L size=100x100 at"
+        assert repr(im).startswith("<PIL.Image.Image image mode=L size=100x100 at")
         assert im.mode == "L"
         assert im.size == (100, 100)
 
         im = Image.new("RGB", (100, 100))
-        assert repr(im)[:45] == "<PIL.Image.Image image mode=RGB size=100x100 "
+        assert repr(im).startswith("<PIL.Image.Image image mode=RGB size=100x100 ")
         assert im.mode == "RGB"
         assert im.size == (100, 100)
 

docs/example/DdsImagePlugin.py

@@ -285,7 +285,7 @@ def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == b"DDS "
+    return prefix.startswith(b"DDS ")
 
 
 Image.register_open(DdsImageFile.format, DdsImageFile, _accept)

docs/handbook/writing-your-own-image-plugin.rst

@@ -54,7 +54,7 @@ true color.
 
 
     def _accept(prefix: bytes) -> bool:
-        return prefix[:4] == b"SPAM"
+        return prefix.startswith(b"SPAM")
 
 
     class SpamImageFile(ImageFile.ImageFile):

src/PIL/BdfFontFile.py

@@ -43,15 +43,15 @@ def bdf_char(
         s = f.readline()
         if not s:
             return None
-        if s[:9] == b"STARTCHAR":
+        if s.startswith(b"STARTCHAR"):
             break
     id = s[9:].strip().decode("ascii")
 
     # load symbol properties
     props = {}
     while True:
         s = f.readline()
-        if not s or s[:6] == b"BITMAP":
+        if not s or s.startswith(b"BITMAP"):
             break
         i = s.find(b" ")
         props[s[:i].decode("ascii")] = s[i + 1 : -1].decode("ascii")
@@ -60,7 +60,7 @@ def bdf_char(
     bitmap = bytearray()
     while True:
         s = f.readline()
-        if not s or s[:7] == b"ENDCHAR":
+        if not s or s.startswith(b"ENDCHAR"):
             break
         bitmap += s[:-1]
 
@@ -96,7 +96,7 @@ def __init__(self, fp: BinaryIO) -> None:
         super().__init__()
 
         s = fp.readline()
-        if s[:13] != b"STARTFONT 2.1":
+        if not s.startswith(b"STARTFONT 2.1"):
             msg = "not a valid BDF file"
             raise SyntaxError(msg)
 
@@ -105,7 +105,7 @@ def __init__(self, fp: BinaryIO) -> None:
 
         while True:
             s = fp.readline()
-            if not s or s[:13] == b"ENDPROPERTIES":
+            if not s or s.startswith(b"ENDPROPERTIES"):
                 break
             i = s.find(b" ")
             props[s[:i].decode("ascii")] = s[i + 1 : -1].decode("ascii")

src/PIL/BlpImagePlugin.py

@@ -246,7 +246,7 @@ class BLPFormatError(NotImplementedError):
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] in (b"BLP1", b"BLP2")
+    return prefix.startswith((b"BLP1", b"BLP2"))
 
 
 class BlpImageFile(ImageFile.ImageFile):

src/PIL/BmpImagePlugin.py

@@ -50,7 +50,7 @@
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:2] == b"BM"
+    return prefix.startswith(b"BM")
 
 
 def _dib_accept(prefix: bytes) -> bool:

src/PIL/BufrStubImagePlugin.py

@@ -33,7 +33,7 @@ def register_handler(handler: ImageFile.StubHandler | None) -> None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == b"BUFR" or prefix[:4] == b"ZCZC"
+    return prefix.startswith((b"BUFR", b"ZCZC"))
 
 
 class BufrStubImageFile(ImageFile.StubImageFile):

src/PIL/CurImagePlugin.py

@@ -26,7 +26,7 @@
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == b"\0\0\2\0"
+    return prefix.startswith(b"\0\0\2\0")
 
 
 ##

src/PIL/DdsImagePlugin.py

@@ -564,7 +564,7 @@ def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == b"DDS "
+    return prefix.startswith(b"DDS ")
 
 
 Image.register_open(DdsImageFile.format, DdsImageFile, _accept)

src/PIL/EpsImagePlugin.py

@@ -170,7 +170,9 @@ def Ghostscript(
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == b"%!PS" or (len(prefix) >= 4 and i32(prefix) == 0xC6D3D0C5)
+    return prefix.startswith(b"%!PS") or (
+        len(prefix) >= 4 and i32(prefix) == 0xC6D3D0C5
+    )
 
 
 ##
@@ -295,7 +297,7 @@ def read_comment(s: str) -> bool:
                     m = field.match(s)
                     if m:
                         k = m.group(1)
-                        if k[:8] == "PS-Adobe":
+                        if k.startswith("PS-Adobe"):
                             self.info["PS-Adobe"] = k[9:]
                         else:
                             self.info[k] = ""

src/PIL/FitsImagePlugin.py

@@ -17,7 +17,7 @@
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:6] == b"SIMPLE"
+    return prefix.startswith(b"SIMPLE")
 
 
 class FitsImageFile(ImageFile.ImageFile):

src/PIL/FpxImagePlugin.py

@@ -42,7 +42,7 @@
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:8] == olefile.MAGIC
+    return prefix.startswith(olefile.MAGIC)
 
 
 ##

src/PIL/FtexImagePlugin.py

@@ -108,7 +108,7 @@ def load_seek(self, pos: int) -> None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == MAGIC
+    return prefix.startswith(MAGIC)
 
 
 Image.register_open(FtexImageFile.format, FtexImageFile, _accept)

src/PIL/GifImagePlugin.py

@@ -67,7 +67,7 @@ class LoadingStrategy(IntEnum):
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:6] in [b"GIF87a", b"GIF89a"]
+    return prefix.startswith((b"GIF87a", b"GIF89a"))
 
 
 ##
@@ -257,7 +257,7 @@ def _seek(self, frame: int, update_image: bool = True) -> None:
                     # application extension
                     #
                     info["extension"] = block, self.fp.tell()
-                    if block[:11] == b"NETSCAPE2.0":
+                    if block.startswith(b"NETSCAPE2.0"):
                         block = self.data()
                         if block and len(block) >= 3 and block[0] == 1:
                             self.info["loop"] = i16(block, 1)

src/PIL/GimpGradientFile.py

@@ -116,7 +116,7 @@ class GimpGradientFile(GradientFile):
     """File handler for GIMP's gradient format."""
 
     def __init__(self, fp: IO[bytes]) -> None:
-        if fp.readline()[:13] != b"GIMP Gradient":
+        if not fp.readline().startswith(b"GIMP Gradient"):
             msg = "not a GIMP gradient file"
             raise SyntaxError(msg)
 

src/PIL/GimpPaletteFile.py

@@ -29,7 +29,7 @@ class GimpPaletteFile:
     def __init__(self, fp: IO[bytes]) -> None:
         palette = [o8(i) * 3 for i in range(256)]
 
-        if fp.readline()[:12] != b"GIMP Palette":
+        if not fp.readline().startswith(b"GIMP Palette"):
             msg = "not a GIMP palette file"
             raise SyntaxError(msg)
 

src/PIL/GribStubImagePlugin.py

@@ -33,7 +33,7 @@ def register_handler(handler: ImageFile.StubHandler | None) -> None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == b"GRIB" and prefix[7] == 1
+    return prefix.startswith(b"GRIB") and prefix[7] == 1
 
 
 class GribStubImageFile(ImageFile.StubImageFile):

src/PIL/Hdf5StubImagePlugin.py

@@ -33,7 +33,7 @@ def register_handler(handler: ImageFile.StubHandler | None) -> None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:8] == b"\x89HDF\r\n\x1a\n"
+    return prefix.startswith(b"\x89HDF\r\n\x1a\n")
 
 
 class HDF5StubImageFile(ImageFile.StubImageFile):

src/PIL/IcnsImagePlugin.py

@@ -117,14 +117,14 @@ def read_png_or_jpeg2000(
     sig = fobj.read(12)
 
     im: Image.Image
-    if sig[:8] == b"\x89PNG\x0d\x0a\x1a\x0a":
+    if sig.startswith(b"\x89PNG\x0d\x0a\x1a\x0a"):
         fobj.seek(start)
         im = PngImagePlugin.PngImageFile(fobj)
         Image._decompression_bomb_check(im.size)
         return {"RGBA": im}
     elif (
-        sig[:4] == b"\xff\x4f\xff\x51"
-        or sig[:4] == b"\x0d\x0a\x87\x0a"
+        sig.startswith(b"\xff\x4f\xff\x51")
+        or sig.startswith(b"\x0d\x0a\x87\x0a")
         or sig == b"\x00\x00\x00\x0cjP  \x0d\x0a\x87\x0a"
     ):
         if not enable_jpeg2k:
@@ -387,7 +387,7 @@ def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == MAGIC
+    return prefix.startswith(MAGIC)
 
 
 Image.register_open(IcnsImageFile.format, IcnsImageFile, _accept)

src/PIL/IcoImagePlugin.py

@@ -118,7 +118,7 @@ def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return prefix[:4] == _MAGIC
+    return prefix.startswith(_MAGIC)
 
 
 class IconHeader(NamedTuple):

src/PIL/ImImagePlugin.py

@@ -155,9 +155,9 @@ def _open(self) -> None:
                 msg = "not an IM file"
                 raise SyntaxError(msg)
 
-            if s[-2:] == b"\r\n":
+            if s.endswith(b"\r\n"):
                 s = s[:-2]
-            elif s[-1:] == b"\n":
+            elif s.endswith(b"\n"):
                 s = s[:-1]
 
             try:
@@ -209,7 +209,7 @@ def _open(self) -> None:
         self._mode = self.info[MODE]
 
         # Skip forward to start of image data
-        while s and s[:1] != b"\x1a":
+        while s and not s.startswith(b"\x1a"):
             s = self.fp.read(1)
         if not s:
             msg = "File truncated"
@@ -247,7 +247,7 @@ def _open(self) -> None:
 
         self._fp = self.fp  # FIXME: hack
 
-        if self.rawmode[:2] == "F;":
+        if self.rawmode.startswith("F;"):
             # ifunc95 formats
             try:
                 # use bit decoder (if necessary)

src/PIL/Image.py

@@ -3998,7 +3998,7 @@ def get_ifd(self, tag: int) -> dict[int, Any]:
                 if tag == ExifTags.IFD.MakerNote:
                     from .TiffImagePlugin import ImageFileDirectory_v2
 
-                    if tag_data[:8] == b"FUJIFILM":
+                    if tag_data.startswith(b"FUJIFILM"):
                         ifd_offset = i32le(tag_data, 8)
                         ifd_data = tag_data[ifd_offset:]
 

src/PIL/Jpeg2KImagePlugin.py

@@ -352,9 +352,8 @@ def load(self) -> Image.core.PixelAccess | None:
 
 
 def _accept(prefix: bytes) -> bool:
-    return (
-        prefix[:4] == b"\xff\x4f\xff\x51"
-        or prefix[:12] == b"\x00\x00\x00\x0cjP  \x0d\x0a\x87\x0a"
+    return prefix.startswith(
+        (b"\xff\x4f\xff\x51", b"\x00\x00\x00\x0cjP  \x0d\x0a\x87\x0a")
     )