Fix lint errors to enable stricter PyLint rules

webrtc/modules/video_coding/codecs/test/plot_webrtc_test_logs.py

 #  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 #
 #  Use of this source code is governed by a BSD-style license
 #  that can be found in the LICENSE file in the root of the source
 #  tree. An additional intellectual property rights grant can be found
 #  in the file PATENTS.  All contributing project authors may
 #  be found in the AUTHORS file in the root of the source tree.
 
 """Plots statistics from WebRTC integration test logs.
 
@@ skipping 98 matching lines @@
 
   Args:
     filename: The name of the file.
     setting: Name of setting to parse (e.g. width).
 
   Returns:
     A list holding parsed settings, e.g. ['width: 128.0', 'width: 160.0'] """
 
   settings = []
 
-  f = open(filename)
+  settings_file = open(filename)
   while True:
-    line = f.readline()
+    line = settings_file.readline()
     if not line:
       break
     if re.search(r'%s' % EVENT_START, line):
       # Parse event.
       parsed = {}
       while True:
-        line = f.readline()
+        line = settings_file.readline()
         if not line:
           break
         if re.search(r'%s' % EVENT_END, line):
           # Add parsed setting to list.
           if setting in parsed:
             s = setting + ': ' + str(parsed[setting])
             if s not in settings:
               settings.append(s)
           break
 
-        TryFindMetric(parsed, line, f)
+        TryFindMetric(parsed, line, settings_file)
 
-  f.close()
+  settings_file.close()
   return settings
 
 
 def ParseMetrics(filename, setting1, setting2):
   """Parses metrics from file.
 
   Args:
     filename: The name of the file.
     setting1: First setting for sorting metrics (e.g. width).
     setting2: Second setting for sorting metrics (e.g. CPU cores used).
@@ skipping 22 matching lines @@
       "encode time (us)": [0.857897, 0.91608, 0.959173, 0.971116, 0.980961],
       "PSNR (dB)": [30.243646, 33.375592, 37.574387, 39.42184, 41.437897],
       "bitrate (kbps)": [50, 100, 300, 500, 1000]
     },
   }
   } """
 
   metrics = {}
 
   # Parse events.
-  f = open(filename)
+  settings_file = open(filename)
   while True:
-    line = f.readline()
+    line = settings_file.readline()
     if not line:
       break
     if re.search(r'%s' % EVENT_START, line):
       # Parse event.
       parsed = {}
       while True:
-        line = f.readline()
+        line = settings_file.readline()
         if not line:
           break
         if re.search(r'%s' % EVENT_END, line):
           # Add parsed values to metrics.
           key1 = setting1 + ': ' + str(parsed[setting1])
           key2 = setting2 + ': ' + str(parsed[setting2])
           if key1 not in metrics:
             metrics[key1] = {}
           if key2 not in metrics[key1]:
             metrics[key1][key2] = {}
 
           for label in parsed:
             if label not in metrics[key1][key2]:
               metrics[key1][key2][label] = []
             metrics[key1][key2][label].append(parsed[label])
 
           break
 
-        TryFindMetric(parsed, line, f)
+        TryFindMetric(parsed, line, settings_file)
 
-  f.close()
+  settings_file.close()
   return metrics
 
 
-def TryFindMetric(parsed, line, f):
+def TryFindMetric(parsed, line, settings_file):
   for metric in METRICS_TO_PARSE:
     name = metric[0]
     label = metric[1]
     if re.search(r'%s' % name, line):
       found, value = GetMetric(name, line)
       if not found:
         # TODO(asapersson): Change format.
         # Try find min, max, average stats.
-        found, minimum = GetMetric("Min", f.readline())
+        found, minimum = GetMetric("Min", settings_file.readline())
         if not found:
           return
-        found, maximum = GetMetric("Max", f.readline())
+        found, maximum = GetMetric("Max", settings_file.readline())
         if not found:
           return
-        found, average = GetMetric("Average", f.readline())
+        found, average = GetMetric("Average", settings_file.readline())
         if not found:
           return
 
         parsed[label + ' min'] = minimum
         parsed[label + ' max'] = maximum
         parsed[label + ' avg'] = average
 
       parsed[label] = value
       return
 
@@ skipping 186 matching lines @@
   figsize[1] *= FIG_SIZE_SCALE_FACTOR_Y
   plt.rcParams["figure.figsize"] = figsize
 
   PlotFigure(sub_keys, y_metrics, x_metric, metrics, GetTitle(filename))
 
   plt.show()
 
 
 if __name__ == '__main__':
   main()