--- a/multimerge.py	Mon Feb 28 18:17:20 2022 +0200
+++ b/multimerge.py	Fri Jun 24 18:55:34 2022 +0300
@@ -145,7 +145,7 @@
 ## Dump/print a given list of events for debugging purposes
 def gcm_dump_events(events, show):
     for event in events:
-        if show == None or show(event):
+        if show is None or show(event):
             ev_start = event["start"].get("dateTime", event["start"].get("date")) if "start" in event else "?"
             ev_end = event["end"].get("dateTime", event["end"].get("date")) if "end" in event else "?"
             summary = event["summary"] if "summary" in event else "?"
@@ -209,7 +209,7 @@
 ###
 class GCMColor():
     def __init__(self, src = None):
-        if src == None:
+        if src is None:
             self.r = self.g = self.b = 0
         elif isinstance(src, str):
             if len(src) == 6:
@@ -326,7 +326,7 @@
         return isinstance(mvalue, str)
 
     def is_string(self, mvalue):
-        return mvalue == None or self.is_str(mvalue)
+        return mvalue is None or self.is_str(mvalue)
 
     def is_log_level(self, mvalue):
         if not self.is_str(mvalue):
@@ -389,14 +389,14 @@
             return re.match("^.*?\s+<[a-z0-9]+[a-z0-9\.\+\-]*\@[a-z0-9]+[a-z0-9\.\-]+>\s*$|[a-z0-9]+[a-z0-9\.\+\-]*\@[a-z0-9]+[a-z0-9\.\-]+", mvalue, flags=re.IGNORECASE)
 
     def trans_email_list(self, mvalue):
-        if mvalue == None:
+        if mvalue is None:
             return mvalue
         else:
             return self.trans_list(mvalue.strip())
 
     def is_email_list(self, mvalue):
         mvalue = self.trans_email_list(mvalue)
-        if mvalue != None:
+        if mvalue is not None:
             for email in mvalue:
                 if not self.is_email(email):
                     gcm_fatal("Invalid e-mail address '{0}' in list {1}.".format(email, ", ".join(mvalue)))
@@ -480,11 +480,11 @@
 
 ## Validate settings
 if cfg.email != "off":
-    if cfg.email_subject == None or len(cfg.email_subject) == 0:
+    if cfg.email_subject is None or len(cfg.email_subject) == 0:
         gcm_fatal("E-mail enabled but email_subject not set.")
-    elif cfg.email_sender == None:
+    elif cfg.email_sender is None:
         gcm_fatal("E-mail enabled but email_sender not set.")
-    elif cfg.email_to == None:
+    elif cfg.email_to is None:
         gcm_fatal("E-mail enabled but email_to not set.")
     else:
         cfg.mset("email_ok", True)
@@ -600,7 +600,7 @@
         for event in events:
             # Set summary and color for existing events
             if event["status"] != "cancelled":
-                if c_found != None:
+                if c_found is not None:
                     event["colorId"] = c_found
                 if "summary" in event:
                     event["summary"] = "[{1}] {0}".format(event["summary"], calendar["gcm_id"])