Use list comprehensions to create transformed lists

Tests/test_file_apng.py

@@ -356,9 +356,7 @@ def test_apng_save(tmp_path):
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/single_frame_default.png") as im:
-        frames = []
-        for frame_im in ImageSequence.Iterator(im):
-            frames.append(frame_im.copy())
+        frames = [frame_im.copy() for frame_im in ImageSequence.Iterator(im)]
         frames[0].save(
             test_file, save_all=True, default_image=True, append_images=frames[1:]
         )

src/PIL/FpxImagePlugin.py

@@ -97,16 +97,15 @@ def _open_index(self, index=1):
 
         s = prop[0x2000002 | id]
 
-        colors = []
         bands = i32(s, 4)
         if bands > 4:
             msg = "Invalid number of bands"
             raise OSError(msg)
-        for i in range(bands):
-            # note: for now, we ignore the "uncalibrated" flag
-            colors.append(i32(s, 8 + i * 4) & 0x7FFFFFFF)
 
-        self._mode, self.rawmode = MODES[tuple(colors)]
+        # note: for now, we ignore the "uncalibrated" flag
+        colors = tuple(i32(s, 8 + i * 4) & 0x7FFFFFFF for i in range(bands))
+
+        self._mode, self.rawmode = MODES[colors]
 
         # load JPEG tables, if any
         self.jpeg = {}

src/PIL/Image.py

@@ -1288,9 +1288,9 @@ def filter(self, filter):
         if self.im.bands == 1 or multiband:
             return self._new(filter.filter(self.im))
 
-        ims = []
-        for c in range(self.im.bands):
-            ims.append(self._new(filter.filter(self.im.getband(c))))
+        ims = [
+            self._new(filter.filter(self.im.getband(c))) for c in range(self.im.bands)
+        ]
         return merge(self.mode, ims)
 
     def getbands(self):
@@ -1339,10 +1339,7 @@ def getcolors(self, maxcolors=256):
         self.load()
         if self.mode in ("1", "L", "P"):
             h = self.im.histogram()
-            out = []
-            for i in range(256):
-                if h[i]:
-                    out.append((h[i], i))
+            out = [(h[i], i) for i in range(256) if h[i]]
             if len(out) > maxcolors:
                 return None
             return out
@@ -1383,10 +1380,7 @@ def getextrema(self):
 
         self.load()
         if self.im.bands > 1:
-            extrema = []
-            for i in range(self.im.bands):
-                extrema.append(self.im.getband(i).getextrema())
-            return tuple(extrema)
+            return tuple(self.im.getband(i).getextrema() for i in range(self.im.bands))
         return self.im.getextrema()
 
     def _getxmp(self, xmp_tags):

src/PIL/ImageCms.py

@@ -787,11 +787,8 @@ def getProfileInfo(profile):
         # info was description \r\n\r\n copyright \r\n\r\n K007 tag \r\n\r\n whitepoint
         description = profile.profile.profile_description
         cpright = profile.profile.copyright
-        arr = []
-        for elt in (description, cpright):
-            if elt:
-                arr.append(elt)
-        return "\r\n\r\n".join(arr) + "\r\n\r\n"
+        elements = [element for element in (description, cpright) if element]
+        return "\r\n\r\n".join(elements) + "\r\n\r\n"
 
     except (AttributeError, OSError, TypeError, ValueError) as v:
         raise PyCMSError(v) from v

src/PIL/ImageOps.py

@@ -557,9 +557,7 @@ def invert(image):
     :param image: The image to invert.
     :return: An image.
     """
-    lut = []
-    for i in range(256):
-        lut.append(255 - i)
+    lut = list(range(255, -1, -1))
     return image.point(lut) if image.mode == "1" else _lut(image, lut)
 
 
@@ -581,10 +579,8 @@ def posterize(image, bits):
     :param bits: The number of bits to keep for each channel (1-8).
     :return: An image.
     """
-    lut = []
     mask = ~(2 ** (8 - bits) - 1)
-    for i in range(256):
-        lut.append(i & mask)
+    lut = [i & mask for i in range(256)]
     return _lut(image, lut)
 
 

src/PIL/ImagePalette.py

@@ -200,21 +200,15 @@ def raw(rawmode, data):
 
 
 def make_linear_lut(black, white):
-    lut = []
     if black == 0:
-        for i in range(256):
-            lut.append(white * i // 255)
-    else:
-        msg = "unavailable when black is non-zero"
-        raise NotImplementedError(msg)  # FIXME
-    return lut
+        return [white * i // 255 for i in range(256)]
+
+    msg = "unavailable when black is non-zero"
+    raise NotImplementedError(msg)  # FIXME
 
 
 def make_gamma_lut(exp):
-    lut = []
-    for i in range(256):
-        lut.append(int(((i / 255.0) ** exp) * 255.0 + 0.5))
-    return lut
+    return [int(((i / 255.0) ** exp) * 255.0 + 0.5) for i in range(256)]
 
 
 def negative(mode="RGB"):
@@ -226,9 +220,7 @@ def negative(mode="RGB"):
 def random(mode="RGB"):
     from random import randint
 
-    palette = []
-    for i in range(256 * len(mode)):
-        palette.append(randint(0, 255))
+    palette = [randint(0, 255) for i in range(256 * len(mode))]
     return ImagePalette(mode, palette)
 
 

src/PIL/ImageQt.py

@@ -103,12 +103,10 @@ def align8to32(bytes, width, mode):
     if not extra_padding:
         return bytes
 
-    new_data = []
-    for i in range(len(bytes) // bytes_per_line):
-        new_data.append(
-            bytes[i * bytes_per_line : (i + 1) * bytes_per_line]
-            + b"\x00" * extra_padding
-        )
+    new_data = [
+        bytes[i * bytes_per_line : (i + 1) * bytes_per_line] + b"\x00" * extra_padding
+        for i in range(len(bytes) // bytes_per_line)
+    ]
 
     return b"".join(new_data)
 
@@ -131,15 +129,11 @@ def _toqclass_helper(im):
         format = qt_format.Format_Mono
     elif im.mode == "L":
         format = qt_format.Format_Indexed8
-        colortable = []
-        for i in range(256):
-            colortable.append(rgb(i, i, i))
+        colortable = [rgb(i, i, i) for i in range(256)]
     elif im.mode == "P":
         format = qt_format.Format_Indexed8
-        colortable = []
         palette = im.getpalette()
-        for i in range(0, len(palette), 3):
-            colortable.append(rgb(*palette[i : i + 3]))
+        colortable = [rgb(*palette[i : i + 3]) for i in range(0, len(palette), 3)]
     elif im.mode == "RGB":
         # Populate the 4th channel with 255
         im = im.convert("RGBA")

src/PIL/ImageStat.py

@@ -59,14 +59,10 @@ def minmax(histogram):
                     x = max(x, i)
             return n, x  # returns (255, 0) if there's no data in the histogram
 
-        v = []
-        for i in range(0, len(self.h), 256):
-            v.append(minmax(self.h[i:]))
-        return v
+        return [minmax(self.h[i:]) for i in range(0, len(self.h), 256)]
 
     def _getcount(self):
         """Get total number of pixels in each layer"""
-
         return [sum(self.h[i : i + 256]) for i in range(0, len(self.h), 256)]
 
     def _getsum(self):
@@ -93,11 +89,7 @@ def _getsum2(self):
 
     def _getmean(self):
         """Get average pixel level for each layer"""
-
-        v = []
-        for i in self.bands:
-            v.append(self.sum[i] / self.count[i])
-        return v
+        return [self.sum[i] / self.count[i] for i in self.bands]
 
     def _getmedian(self):
         """Get median pixel level for each layer"""
@@ -116,28 +108,18 @@ def _getmedian(self):
 
     def _getrms(self):
         """Get RMS for each layer"""
-
-        v = []
-        for i in self.bands:
-            v.append(math.sqrt(self.sum2[i] / self.count[i]))
-        return v
+        return [math.sqrt(self.sum2[i] / self.count[i]) for i in self.bands]
 
     def _getvar(self):
         """Get variance for each layer"""
-
-        v = []
-        for i in self.bands:
-            n = self.count[i]
-            v.append((self.sum2[i] - (self.sum[i] ** 2.0) / n) / n)
-        return v
+        return [
+            (self.sum2[i] - (self.sum[i] ** 2.0) / self.count[i]) / self.count[i]
+            for i in self.bands
+        ]
 
     def _getstddev(self):
         """Get standard deviation for each layer"""
-
-        v = []
-        for i in self.bands:
-            v.append(math.sqrt(self.var[i]))
-        return v
+        return [math.sqrt(self.var[i]) for i in self.bands]
 
 
 Global = Stat  # compatibility

src/PIL/JpegImagePlugin.py

@@ -233,9 +233,7 @@ def SOF(self, marker):
         # fixup icc profile
         self.icclist.sort()  # sort by sequence number
         if self.icclist[0][13] == len(self.icclist):
-            profile = []
-            for p in self.icclist:
-                profile.append(p[14:])
+            profile = [p[14:] for p in self.icclist]
             icc_profile = b"".join(profile)
         else:
             icc_profile = None  # wrong number of fragments

src/PIL/MicImagePlugin.py

@@ -51,10 +51,11 @@ def _open(self):
         # find ACI subfiles with Image members (maybe not the
         # best way to identify MIC files, but what the... ;-)
 
-        self.images = []
-        for path in self.ole.listdir():
-            if path[1:] and path[0][-4:] == ".ACI" and path[1] == "Image":
-                self.images.append(path)
+        self.images = [
+            path
+            for path in self.ole.listdir()
+            if path[1:] and path[0][-4:] == ".ACI" and path[1] == "Image"
+        ]
 
         # if we didn't find any images, this is probably not
         # an MIC file.

src/PIL/PcfFontFile.py

@@ -129,9 +129,8 @@ def _load_properties(self):
         nprops = i32(fp.read(4))
 
         # read property description
-        p = []
-        for i in range(nprops):
-            p.append((i32(fp.read(4)), i8(fp.read(1)), i32(fp.read(4))))
+        p = [(i32(fp.read(4)), i8(fp.read(1)), i32(fp.read(4))) for _ in range(nprops)]
+
         if nprops & 3:
             fp.seek(4 - (nprops & 3), io.SEEK_CUR)  # pad
 
@@ -186,8 +185,6 @@ def _load_bitmaps(self, metrics):
         #
         # bitmap data
 
-        bitmaps = []
-
         fp, format, i16, i32 = self._getformat(PCF_BITMAPS)
 
         nbitmaps = i32(fp.read(4))
@@ -196,13 +193,9 @@ def _load_bitmaps(self, metrics):
             msg = "Wrong number of bitmaps"
             raise OSError(msg)
 
-        offsets = []
-        for i in range(nbitmaps):
-            offsets.append(i32(fp.read(4)))
+        offsets = [i32(fp.read(4)) for _ in range(nbitmaps)]
 
-        bitmap_sizes = []
-        for i in range(4):
-            bitmap_sizes.append(i32(fp.read(4)))
+        bitmap_sizes = [i32(fp.read(4)) for _ in range(4)]
 
         # byteorder = format & 4  # non-zero => MSB
         bitorder = format & 8  # non-zero => MSB
@@ -218,6 +211,7 @@ def _load_bitmaps(self, metrics):
         if bitorder:
             mode = "1"
 
+        bitmaps = []
         for i in range(nbitmaps):
             xsize, ysize = metrics[i][:2]
             b, e = offsets[i : i + 2]

src/PIL/SpiderImagePlugin.py

@@ -238,9 +238,7 @@ def makeSpiderHeader(im):
     if nvalues < 23:
         return []
 
-    hdr = []
-    for i in range(nvalues):
-        hdr.append(0.0)
+    hdr = [0.0] * nvalues
 
     # NB these are Fortran indices
     hdr[1] = 1.0  # nslice (=1 for an image)