diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index da63148..4cf67ac 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -623,42 +623,42 @@
             """Construct and return tupel with IO objects:
             p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
             """
-            if stdin == None and stdout == None and stderr == None:
+            if stdin is None and stdout is None and stderr is None:
                 return (None, None, None, None, None, None)
 
             p2cread, p2cwrite = None, None
             c2pread, c2pwrite = None, None
             errread, errwrite = None, None
 
-            if stdin == None:
+            if stdin is None:
                 p2cread = GetStdHandle(STD_INPUT_HANDLE)
             elif stdin == PIPE:
                 p2cread, p2cwrite = CreatePipe(None, 0)
                 # Detach and turn into fd
                 p2cwrite = p2cwrite.Detach()
                 p2cwrite = msvcrt.open_osfhandle(p2cwrite, 0)
-            elif type(stdin) == int:
+            elif isinstance(stdin, int):
                 p2cread = msvcrt.get_osfhandle(stdin)
             else:
                 # Assuming file-like object
                 p2cread = msvcrt.get_osfhandle(stdin.fileno())
             p2cread = self._make_inheritable(p2cread)
 
-            if stdout == None:
+            if stdout is None:
                 c2pwrite = GetStdHandle(STD_OUTPUT_HANDLE)
             elif stdout == PIPE:
                 c2pread, c2pwrite = CreatePipe(None, 0)
                 # Detach and turn into fd
                 c2pread = c2pread.Detach()
                 c2pread = msvcrt.open_osfhandle(c2pread, 0)
-            elif type(stdout) == int:
+            elif isinstance(stdout, int):
                 c2pwrite = msvcrt.get_osfhandle(stdout)
             else:
                 # Assuming file-like object
                 c2pwrite = msvcrt.get_osfhandle(stdout.fileno())
             c2pwrite = self._make_inheritable(c2pwrite)
 
-            if stderr == None:
+            if stderr is None:
                 errwrite = GetStdHandle(STD_ERROR_HANDLE)
             elif stderr == PIPE:
                 errread, errwrite = CreatePipe(None, 0)
@@ -667,7 +667,7 @@
                 errread = msvcrt.open_osfhandle(errread, 0)
             elif stderr == STDOUT:
                 errwrite = c2pwrite
-            elif type(stderr) == int:
+            elif isinstance(stderr, int):
                 errwrite = msvcrt.get_osfhandle(stderr)
             else:
                 # Assuming file-like object
@@ -715,7 +715,7 @@
 
             # Process startup details
             default_startupinfo = STARTUPINFO()
-            if startupinfo == None:
+            if startupinfo is None:
                 startupinfo = default_startupinfo
             if not None in (p2cread, c2pwrite, errwrite):
                 startupinfo.dwFlags |= STARTF_USESTDHANDLES
@@ -774,18 +774,18 @@
             # output pipe are maintained in this process or else the
             # pipe will not close when the child process exits and the
             # ReadFile will hang.
-            if p2cread != None:
+            if p2cread is not None:
                 p2cread.Close()
-            if c2pwrite != None:
+            if c2pwrite is not None:
                 c2pwrite.Close()
-            if errwrite != None:
+            if errwrite is not None:
                 errwrite.Close()
 
 
         def poll(self):
             """Check if child process has terminated.  Returns returncode
             attribute."""
-            if self.returncode == None:
+            if self.returncode is None:
                 if WaitForSingleObject(self._handle, 0) == WAIT_OBJECT_0:
                     self.returncode = GetExitCodeProcess(self._handle)
                     _active.remove(self)
@@ -795,7 +795,7 @@
         def wait(self):
             """Wait for child process to terminate.  Returns returncode
             attribute."""
-            if self.returncode == None:
+            if self.returncode is None:
                 obj = WaitForSingleObject(self._handle, INFINITE)
                 self.returncode = GetExitCodeProcess(self._handle)
                 _active.remove(self)
@@ -831,7 +831,7 @@
                 stderr_thread.start()
 
             if self.stdin:
-                if input != None:
+                if input is not None:
                     self.stdin.write(input)
                 self.stdin.close()
 
@@ -841,9 +841,9 @@
                 stderr_thread.join()
 
             # All data exchanged.  Translate lists into strings.
-            if stdout != None:
+            if stdout is not None:
                 stdout = stdout[0]
-            if stderr != None:
+            if stderr is not None:
                 stderr = stderr[0]
 
             # Translate newlines, if requested.  We cannot let the file
@@ -871,33 +871,33 @@
             c2pread, c2pwrite = None, None
             errread, errwrite = None, None
 
-            if stdin == None:
+            if stdin is None:
                 pass
             elif stdin == PIPE:
                 p2cread, p2cwrite = os.pipe()
-            elif type(stdin) == int:
+            elif isinstance(stdin, int):
                 p2cread = stdin
             else:
                 # Assuming file-like object
                 p2cread = stdin.fileno()
 
-            if stdout == None:
+            if stdout is None:
                 pass
             elif stdout == PIPE:
                 c2pread, c2pwrite = os.pipe()
-            elif type(stdout) == int:
+            elif isinstance(stdout, int):
                 c2pwrite = stdout
             else:
                 # Assuming file-like object
                 c2pwrite = stdout.fileno()
 
-            if stderr == None:
+            if stderr is None:
                 pass
             elif stderr == PIPE:
                 errread, errwrite = os.pipe()
             elif stderr == STDOUT:
                 errwrite = c2pwrite
-            elif type(stderr) == int:
+            elif isinstance(stderr, int):
                 errwrite = stderr
             else:
                 # Assuming file-like object
@@ -942,7 +942,7 @@
             if shell:
                 args = ["/bin/sh", "-c"] + args
 
-            if executable == None:
+            if executable is None:
                 executable = args[0]
 
             # For transferring possible exec failure from child to parent
@@ -985,13 +985,13 @@
                     if close_fds:
                         self._close_fds(but=errpipe_write)
 
-                    if cwd != None:
+                    if cwd is not None:
                         os.chdir(cwd)
 
                     if preexec_fn:
                         apply(preexec_fn)
 
-                    if env == None:
+                    if env is None:
                         os.execvp(executable, args)
                     else:
                         os.execvpe(executable, args, env)
@@ -1042,7 +1042,7 @@
         def poll(self):
             """Check if child process has terminated.  Returns returncode
             attribute."""
-            if self.returncode == None:
+            if self.returncode is None:
                 try:
                     pid, sts = os.waitpid(self.pid, os.WNOHANG)
                     if pid == self.pid:
@@ -1055,7 +1055,7 @@
         def wait(self):
             """Wait for child process to terminate.  Returns returncode
             attribute."""
-            if self.returncode == None:
+            if self.returncode is None:
                 pid, sts = os.waitpid(self.pid, 0)
                 self._handle_exitstatus(sts)
             return self.returncode
@@ -1117,9 +1117,9 @@
                     stderr.append(data)
 
             # All data exchanged.  Translate lists into strings.
-            if stdout != None:
+            if stdout is not None:
                 stdout = ''.join(stdout)
-            if stderr != None:
+            if stderr is not None:
                 stderr = ''.join(stderr)
 
             # Translate newlines, if requested.  We cannot let the file