diff --git a/youtube_dl/compat.py b/youtube_dl/compat.py
index 27596687d..f4a85443e 100644
--- a/youtube_dl/compat.py
+++ b/youtube_dl/compat.py
@@ -247,7 +247,7 @@ else:
                 userhome = compat_getenv('HOME')
             elif 'USERPROFILE' in os.environ:
                 userhome = compat_getenv('USERPROFILE')
-            elif not 'HOMEPATH' in os.environ:
+            elif 'HOMEPATH' not in os.environ:
                 return path
             else:
                 try:
diff --git a/youtube_dl/postprocessor/execafterdownload.py b/youtube_dl/postprocessor/execafterdownload.py
index 09db43611..75c0f7bbe 100644
--- a/youtube_dl/postprocessor/execafterdownload.py
+++ b/youtube_dl/postprocessor/execafterdownload.py
@@ -14,7 +14,7 @@ class ExecAfterDownloadPP(PostProcessor):
 
     def run(self, information):
         cmd = self.exec_cmd
-        if not '{}' in cmd:
+        if '{}' not in cmd:
             cmd += ' {}'
 
         cmd = cmd.replace('{}', shlex_quote(information['filepath']))
diff --git a/youtube_dl/update.py b/youtube_dl/update.py
index 4c07a558e..2d2703368 100644
--- a/youtube_dl/update.py
+++ b/youtube_dl/update.py
@@ -79,7 +79,7 @@ def update_self(to_screen, verbose):
             to_screen(compat_str(traceback.format_exc()))
         to_screen('ERROR: can\'t obtain versions info. Please try again later.')
         return
-    if not 'signature' in versions_info:
+    if 'signature' not in versions_info:
         to_screen('ERROR: the versions file is not signed or corrupted. Aborting.')
         return
     signature = versions_info['signature']
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 2e70cc791..a95d2c942 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -1024,7 +1024,7 @@ def smuggle_url(url, data):
 
 
 def unsmuggle_url(smug_url, default=None):
-    if not '#__youtubedl_smuggle' in smug_url:
+    if '#__youtubedl_smuggle' not in smug_url:
         return smug_url, default
     url, _, sdata = smug_url.rpartition('#')
     jsond = compat_parse_qs(sdata)['__youtubedl_smuggle'][0]