diff --git a/PIL/BmpImagePlugin.py b/PIL/BmpImagePlugin.py
index 436ca5dce..cd6dc49a2 100644
--- a/PIL/BmpImagePlugin.py
+++ b/PIL/BmpImagePlugin.py
@@ -133,7 +133,7 @@ class BmpImageFile(ImageFile.ImageFile):
             greyscale = 1
             if colors == 2:
                 indices = (0, 255)
-            elif colors > 2**16 or colors <=0: #We're reading a i32. 
+            elif not 0 < colors <= 2**16: #We're reading a i32. 
                 raise IOError("Unsupported BMP Palette size (%d)" % colors)
             else:
                 indices = list(range(colors))
diff --git a/PIL/IcoImagePlugin.py b/PIL/IcoImagePlugin.py
index 268e93d6c..b7f3cf16a 100644
--- a/PIL/IcoImagePlugin.py
+++ b/PIL/IcoImagePlugin.py
@@ -102,7 +102,7 @@ class IcoFile:
         Get an image from the icon
         """
         for (i, h) in enumerate(self.entry):
-            if size == h['dim'] and (bpp == False or bpp == h['color_depth']):
+            if size == h['dim'] and bpp in (h['color_depth'], False):
                 return self.frame(i)
         return self.frame(0)
 
diff --git a/PIL/ImImagePlugin.py b/PIL/ImImagePlugin.py
index 1f8f011dc..aab0c13a9 100644
--- a/PIL/ImImagePlugin.py
+++ b/PIL/ImImagePlugin.py
@@ -134,7 +134,7 @@ class ImImageFile(ImageFile.ImageFile):
             if s == b"\r":
                 continue
 
-            if not s or s == b'\0' or s == b'\x1A':
+            if not s or s in (b'\0', b'\x1A'):
                 break
 
             # FIXME: this may read whole file if not a text file
@@ -212,7 +212,7 @@ class ImImageFile(ImageFile.ImageFile):
                         linear = 0
                 else:
                     greyscale = 0
-            if self.mode == "L" or self.mode == "LA":
+            if self.mode in ("L", "LA"):
                 if greyscale:
                     if not linear:
                         self.lut = [i8(c) for c in palette[:256]]
@@ -258,7 +258,7 @@ class ImImageFile(ImageFile.ImageFile):
 
     def seek(self, frame):
 
-        if frame < 0 or frame >= self.info[FRAMES]:
+        if not 0 <= frame < self.info[FRAMES]:
             raise EOFError("seek outside sequence")
 
         if self.frame == frame:
diff --git a/PIL/ImageOps.py b/PIL/ImageOps.py
index 0d22f8c64..b0e35fa00 100644
--- a/PIL/ImageOps.py
+++ b/PIL/ImageOps.py
@@ -272,12 +272,12 @@ def fit(image, size, method=Image.NEAREST, bleed=0.0, centering=(0.5, 0.5)):
     if not isinstance(centering, list):
         centering = [centering[0], centering[1]]
 
-    if centering[0] > 1.0 or centering[0] < 0.0:
+    if not 0.0 < centering[0] < 1.0:
         centering [0] = 0.50
-    if centering[1] > 1.0 or centering[1] < 0.0:
+    if not 0.0 < centering[1] < 1.0:
         centering[1] = 0.50
 
-    if bleed > 0.49999 or bleed < 0.0:
+    if not 0.0 < bleed < 0.49999:
         bleed = 0.0
 
     # calculate the area to use for resizing and cropping, subtracting
diff --git a/PIL/IptcImagePlugin.py b/PIL/IptcImagePlugin.py
index 104153002..6de7de466 100644
--- a/PIL/IptcImagePlugin.py
+++ b/PIL/IptcImagePlugin.py
@@ -68,7 +68,7 @@ class IptcImageFile(ImageFile.ImageFile):
         tag = i8(s[1]), i8(s[2])
 
         # syntax
-        if i8(s[0]) != 0x1C or tag[0] < 1 or tag[0] > 9:
+        if i8(s[0]) != 0x1C or not 1 <= tag[0] <= 9:
             raise SyntaxError("invalid IPTC/NAA file")
 
         # field size
diff --git a/PIL/JpegImagePlugin.py b/PIL/JpegImagePlugin.py
index da52006ca..d727863e0 100644
--- a/PIL/JpegImagePlugin.py
+++ b/PIL/JpegImagePlugin.py
@@ -307,7 +307,7 @@ class JpegImageFile(ImageFile.ImageFile):
                     # self.__offset = self.fp.tell()
                     break
                 s = self.fp.read(1)
-            elif i == 0 or i == 65535:
+            elif i in (0, 65535):
                 # padded marker or junk; move on
                 s = "\xff"
             else:
diff --git a/PIL/OleFileIO.py b/PIL/OleFileIO.py
index 8a3c77be4..a75558a5a 100644
--- a/PIL/OleFileIO.py
+++ b/PIL/OleFileIO.py
@@ -699,7 +699,7 @@ class _OleStream(io.BytesIO):
                     debug('sect=ENDOFCHAIN before expected size')
                     raise IOError('incomplete OLE stream')
             # sector index should be within FAT:
-            if sect<0 or sect>=len(fat):
+            if not 0 <= sect < len(fat):
                 debug('sect=%d (%X) / len(fat)=%d' % (sect, sect, len(fat)))
                 debug('i=%d / nb_sectors=%d' %(i, nb_sectors))
 ##                tmp_data = b"".join(data)
@@ -920,7 +920,7 @@ class _OleDirectoryEntry:
         if child_sid == NOSTREAM:
             return
         # check if child SID is in the proper range:
-        if child_sid<0 or child_sid>=len(self.olefile.direntries):
+        if not 0 <= child_sid < len(self.olefile.direntries):
             self.olefile._raise_defect(DEFECT_FATAL, 'OLE DirEntry index out of range')
         # get child direntry:
         child = self.olefile._load_direntry(child_sid) #direntries[child_sid]
@@ -1385,7 +1385,7 @@ class OleFileIO:
         # The FAT is a sector chain starting at the first index of itself.
         for isect in fat1:
             #print("isect = %X" % isect)
-            if isect == ENDOFCHAIN or isect == FREESECT:
+            if isect in (ENDOFCHAIN, FREESECT):
                 # the end of the sector chain has been reached
                 break
             # read the FAT sector
@@ -1572,7 +1572,7 @@ class OleFileIO:
         raise: IOError if the entry has always been referenced.
         """
         # check if SID is OK:
-        if sid<0 or sid>=len(self.direntries):
+        if 0 <= sid < len(self.direntries):
             self._raise_defect(DEFECT_FATAL, "OLE directory index out of range")
         # check if entry was already referenced:
         if self.direntries[sid] is not None:
diff --git a/PIL/PngImagePlugin.py b/PIL/PngImagePlugin.py
index 2bdf74608..619ccfc20 100644
--- a/PIL/PngImagePlugin.py
+++ b/PIL/PngImagePlugin.py
@@ -555,8 +555,9 @@ def _save(im, fp, filename, chunk=putchunk, check=0):
     if im.mode == "P":
         palette_byte_number = (2 ** bits) * 3
         palette_bytes = im.im.getpalette("RGB")[:palette_byte_number]
-        while len(palette_bytes) < palette_byte_number:
-            palette_bytes += b'\0'
+        diff = palette_byte_number - len(palette_bytes)
+        if diff > 0:
+            palette_bytes += b'\0' * diff
         chunk(fp, b"PLTE", palette_bytes)
 
     transparency = im.encoderinfo.get('transparency',im.info.get('transparency', None))
diff --git a/PIL/SgiImagePlugin.py b/PIL/SgiImagePlugin.py
index b60df473c..484f2df72 100644
--- a/PIL/SgiImagePlugin.py
+++ b/PIL/SgiImagePlugin.py
@@ -53,7 +53,7 @@ class SgiImageFile(ImageFile.ImageFile):
         layout = i8(s[3]), i16(s[4:]), i16(s[10:])
 
         # determine mode from bytes/zsize
-        if layout == (1, 2, 1) or layout == (1, 1, 1):
+        if layout in ((1, 2, 1), (1, 1, 1)):
             self.mode = "L"
         elif layout == (1, 3, 3):
             self.mode = "RGB"
diff --git a/PIL/TiffImagePlugin.py b/PIL/TiffImagePlugin.py
index fe658d22c..aab67fe6d 100644
--- a/PIL/TiffImagePlugin.py
+++ b/PIL/TiffImagePlugin.py
@@ -1043,7 +1043,7 @@ def _save(im, fp, filename):
         unit = im.encoderinfo["resolution unit"]
         if unit == "inch":
             ifd[RESOLUTION_UNIT] = 2
-        elif unit == "cm" or unit == "centimeter":
+        elif unit in ("cm", "centimeter"):
             ifd[RESOLUTION_UNIT] = 3
         else:
             ifd[RESOLUTION_UNIT] = 1