Compare with None should be done with 'is [not]', not equality operator.

PEP 8 says:
  Comparisons to singletons like None should always be done with 'is' or 'is not', never the equality operators.

OpenPrintingRequest.py

@@ -62,7 +62,7 @@ def __del__ (self):
 
     def cancel (self):
         debugprint ("%s: cancel()" % self)
-        if self._handle != None:
+        if self._handle is not None:
             self.openprinting.cancelOperation (self._handle)
             self._handle = None
 

PhysicalDevice.py

@@ -60,7 +60,7 @@ def _get_host_from_uri (self, uri):
             if rest.startswith ("/net/"):
                 (rest, ipparam) = urllib.parse.splitquery (rest[5:])
 
-            if ipparam != None:
+            if ipparam is not None:
                 if ipparam.startswith("ip="):
                     hostport = ipparam[3:]
                 elif ipparam.startswith ("hostname="):
@@ -77,7 +77,7 @@ def _get_host_from_uri (self, uri):
             return None, None
         else:
             (hostport, rest) = urllib.parse.splithost (rest)
-            if hostport == None:
+            if hostport is None:
                 return None, None
 
         if hostport:
@@ -90,19 +90,19 @@ def add_device (self, device):
             host, dnssdhost = self._get_host_from_uri (device.uri)
             if (hasattr (device, 'address')):
                 host = device.address
-            if (hasattr (device, 'hostname') and dnssdhost == None):
+            if (hasattr (device, 'hostname') and dnssdhost is None):
                 dnssdhost = device.hostname
-            if (host == None and dnssdhost == None) or \
+            if (host is None and dnssdhost is None) or \
                (host and self._network_host and \
                 host != self._network_host) or \
                (dnssdhost and self.dnssd_hostname and \
                 dnssdhost != self.dnssd_hostname) or \
-               (host == None and self.dnssd_hostname == None) or \
-               (dnssdhost == None and self._network_host == None):
+               (host is None and self.dnssd_hostname is None) or \
+               (dnssdhost is None and self._network_host is None):
                 raise ValueError
         else:
             (mfg, mdl) = self._canonical_id (device)
-            if self.devices == None:
+            if self.devices is None:
                 self.mfg = mfg
                 self.mdl = mdl
                 self.mfg_lower = mfg.lower ()
@@ -157,11 +157,11 @@ def count_lower (s):
             if dnssdhost:
                 self.dnssd_hostname = dnssdhost;
 
-        if (hasattr (device, 'address') and self._network_host == None):
+        if (hasattr (device, 'address') and self._network_host is None):
             address = device.address
             if address:
                 self._network_host = address
-        if (hasattr (device, 'hostname') and self.dnssd_hostname == None):
+        if (hasattr (device, 'hostname') and self.dnssd_hostname is None):
             hostname = device.hostname
             if hostname:
                 self.dnssd_hostname = hostname
@@ -275,10 +275,10 @@ def __lt__(self, other):
             return False
 
         if self._network_host != other._network_host:
-            if self._network_host == None:
+            if self._network_host is None:
                 return True
 
-            if other._network_host == None:
+            if other._network_host is None:
                 return False
 
             return self._network_host < other._network_host

applet.py

@@ -361,7 +361,7 @@ def handle_dbus_signal (self, *args):
     def check_for_jobs (self, *args):
         debugprint ("checking for jobs")
         if any_jobs ():
-            if self.timer != None:
+            if self.timer is not None:
                 GLib.source_remove (self.timer)
 
             self.remove_signal_receiver ()

asyncconn.py

@@ -114,7 +114,7 @@ def __init__ (self, reply_handler=None, error_handler=None,
         self._destroyed = False
 
         # Decide whether to use direct IPP or PolicyKit.
-        if host == None:
+        if host is None:
             host = cups.getServer()
         use_pk = ((host.startswith ('/') or host == 'localhost') and
                   os.getuid () != 0)

asyncipp.py

@@ -71,11 +71,11 @@ def set_auth_info (self, password):
         self._auth_queue.put (password)
 
     def run (self):
-        if self.host == None:
+        if self.host is None:
             self.host = cups.getServer ()
-        if self.port == None:
+        if self.port is None:
             self.port = cups.getPort ()
-        if self._encryption == None:
+        if self._encryption is None:
             self._encryption = cups.getEncryption ()
 
         if self.user:
@@ -100,7 +100,7 @@ def run (self):
             self.idle = self._queue.empty ()
             item = self._queue.get ()
             debugprint ("Next task: %s" % repr (item))
-            if item == None:
+            if item is None:
                 # Our signal to quit.
                 self._queue.task_done ()
                 break
@@ -176,15 +176,15 @@ def stop (self):
     def _auth (self, prompt, conn=None, method=None, resource=None):
         def prompt_auth (prompt):
             Gdk.threads_enter ()
-            if conn == None:
+            if conn is None:
                 self._auth_handler (prompt, self._conn)
             else:
                 self._auth_handler (prompt, self._conn, method, resource)
 
             Gdk.threads_leave ()
             return False
 
-        if self._auth_handler == None:
+        if self._auth_handler is None:
             return ""
 
         GLib.idle_add (prompt_auth, prompt)
@@ -349,7 +349,7 @@ def _destroy (self):
         del self._client_error_handler
 
     def error_handler (self, conn, exc):
-        if self._client_fn == None:
+        if self._client_fn is None:
             # This is the initial "connection" operation, or a
             # subsequent reconnection attempt.
             debugprint ("Connection/reconnection failed")
@@ -433,7 +433,7 @@ def error_handler (self, conn, exc):
 
     def auth_handler (self, prompt, conn, method=None, resource=None):
         if self._auth_called == False:
-            if self._user == None:
+            if self._user is None:
                 self._user = cups.getUser()
             if self._user:
                 host = conn.thread.host
@@ -479,15 +479,15 @@ def auth_handler (self, prompt, conn, method=None, resource=None):
         if conn.semantic:
             op = conn.semantic.current_operation ()
 
-        if op == None:
+        if op is None:
             d = authconn.AuthDialog (parent=conn.parent)
         else:
             title = _("Authentication (%s)") % op
             d = authconn.AuthDialog (title=title,
                                      parent=conn.parent)
 
         d.set_prompt ('')
-        if self._user == None:
+        if self._user is None:
             self._user = cups.getUser()
         d.set_auth_info (['', ''])
         d.field_grab_focus ('username')
@@ -543,7 +543,7 @@ def _reconnect_reply (self, conn, result):
         # so we've reconnected as that user.  Alternatively, the
         # connection has failed and we're retrying.
         debugprint ("Connected as %s" % self._user)
-        if self._client_fn != None:
+        if self._client_fn is not None:
             self.submit_task ()
 
     def _reconnect_error (self, conn, exc):
@@ -556,7 +556,7 @@ def _reconnect_error (self, conn, exc):
         if conn.semantic:
             op = conn.semantic.current_operation ()
 
-        if op == None:
+        if op is None:
             msg = _("CUPS server error")
         else:
             msg = _("CUPS server error (%s)") % op
@@ -567,7 +567,7 @@ def _reconnect_error (self, conn, exc):
                                buttons=Gtk.ButtonsType.NONE,
                                text=msg)
 
-        if self._client_fn == None and type (exc) == RuntimeError:
+        if self._client_fn is None and type (exc) == RuntimeError:
             # This was a connection failure.
             message = 'service-error-service-unavailable'
         elif type (exc) == cups.IPPError:

asyncpk1.py

@@ -242,7 +242,7 @@ def __init__(self, reply_handler=None, error_handler=None,
             self._system_bus = None
 
         global _DevicesGet_uses_new_api
-        if _DevicesGet_uses_new_api == None and self._system_bus:
+        if _DevicesGet_uses_new_api is None and self._system_bus:
             try:
                 obj = self._system_bus.get_object(CUPS_PK_NAME, CUPS_PK_PATH)
                 proxy = dbus.Interface (obj, dbus.INTROSPECTABLE_IFACE)
@@ -324,7 +324,7 @@ def _args_kwds_to_tuple (self, types, params, args, kwds):
             del leftover_kwds["auth_handler"]
 
         result = [True, reply_handler, error_handler, ()]
-        if self._system_bus == None:
+        if self._system_bus is None:
             return result
 
         tup = []
@@ -461,7 +461,7 @@ def _unpack_getDevices_reply (self, dbusdict):
                 else:
                     device_uri = result_str[keywithaffix]
 
-            if device_uri != None:
+            if device_uri is not None:
                 devices[device_uri] = device_dict
 
             n += 1

authconn.py

@@ -43,7 +43,7 @@ def __init__ (self, title=None, parent=None,
                            Gtk.STOCK_OK, Gtk.ResponseType.OK),
                   auth_info_required=None,
                   allow_remember=False):
-        if title == None:
+        if title is None:
             title = _("Authentication")
         if auth_info_required is None:
             auth_info_required = ['username', 'password']
@@ -124,13 +124,13 @@ def __init__ (self):
         self.creds = dict() # by (host,port)
 
     def cache_auth_info (self, data, host=None, port=None):
-        if port == None:
+        if port is None:
             port = 631
 
         self.creds[(host,port)] = data
 
     def lookup_auth_info (self, host=None, port=None):
-        if port == None:
+        if port is None:
             port = 631
 
         try:
@@ -139,7 +139,7 @@ def lookup_auth_info (self, host=None, port=None):
             return None
 
     def remove_auth_info (self, host=None, port=None):
-        if port == None:
+        if port is None:
             port = 631
 
         try:
@@ -152,11 +152,11 @@ def remove_auth_info (self, host=None, port=None):
 class Connection:
     def __init__ (self, parent=None, try_as_root=True, lock=False,
                   host=None, port=None, encryption=None):
-        if host != None:
+        if host is not None:
             cups.setServer (host)
-        if port != None:
+        if port is not None:
             cups.setPort (port)
-        if encryption != None:
+        if encryption is not None:
             cups.setEncryption (encryption)
 
         self._use_password = ''
@@ -341,7 +341,7 @@ def _perform_authentication (self):
         self._passes += 1
 
         creds = global_authinfocache.lookup_auth_info (host=self._server, port=self._port)
-        if creds != None:
+        if creds is not None:
             if (creds[0] != 'root' or self._try_as_root):
                 (self._use_user, self._use_password) = creds
             del creds

check-device-ids.py

@@ -64,7 +64,7 @@
            "by temporarily disabling your firewall (or by allowing\n"
            "incoming UDP packets on port 161).\n")
 
-if devices == None:
+if devices is None:
     if not SPECIFIC_URI:
         print("Examining connected devices")
 
@@ -87,7 +87,7 @@
             sys.exit (1)
 
 if SPECIFIC_URI:
-    if devices.get (SPECIFIC_URI) == None:
+    if devices.get (SPECIFIC_URI) is None:
         devices = { SPECIFIC_URI:
                         { 'device-make-and-model': '',
                           'device-id': ''} }
@@ -123,7 +123,7 @@
                 devs = []
 
                 def got_device (dev):
-                    if dev != None:
+                    if dev is not None:
                         devs.append (dev)
 
                 import probe_printer

cupshelpers/cupshelpers.py

@@ -55,7 +55,7 @@ def __init__(self, name, connection, **kw):
         self._ppd = None # load on demand
 
     def __del__ (self):
-        if self._ppd != None:
+        if self._ppd is not None:
             os.unlink(self._ppd)
 
     def __repr__ (self):
@@ -210,7 +210,7 @@ def getPPD(self):
                 else:
                     raise
 
-        if result == None and self._ppd != None:
+        if result is None and self._ppd is not None:
             result = cups.PPD (self._ppd)
 
         return result
@@ -368,7 +368,7 @@ def jobsQueued(self, only_tests=False, limit=None):
                  attrs['job-name'] == 'Test Page')):
                 ret.append (id)
 
-                if limit != None and len (ret) == limit:
+                if limit is not None and len (ret) == limit:
                     break
         return ret
 
@@ -402,7 +402,7 @@ def jobsPreserved(self, limit=None):
                            cups.IPP_JOB_PENDING) < cups.IPP_JOB_COMPLETED):
                 continue
             ret.append (id)
-            if limit != None and len (ret) == limit:
+            if limit is not None and len (ret) == limit:
                 break
 
         return ret
@@ -546,7 +546,7 @@ def __lt__(self, other):
         """
         Compare devices by order of preference.
         """
-        if other == None:
+        if other is None:
             return True
 
         if self.is_class != other.is_class:
@@ -665,7 +665,7 @@ def activateNewPrinter(connection, name):
     connection.acceptJobs (name)
 
     # Set as the default if there is not already a default printer.
-    if connection.getDefault () == None:
+    if connection.getDefault () is None:
         connection.setDefault (name)
 
 def copyPPDOptions(ppd1, ppd2):