diff --git a/tools/warn/html_writer.py b/tools/warn/html_writer.py
index bed25ed..ac5d4b7 100644
--- a/tools/warn/html_writer.py
+++ b/tools/warn/html_writer.py
@@ -144,12 +144,11 @@
     2D warnings array where warnings[p][s] is # of warnings in project name p of
     severity level s
   """
-  # pylint:disable=invalid-name
   warnings = {p: {s.value: 0 for s in Severity.levels} for p in project_names}
-  for i in warn_patterns:
-    s = i['severity'].value
-    for p in i['projects']:
-      warnings[p][s] += i['projects'][p]
+  for pattern in warn_patterns:
+    value = pattern['severity'].value
+    for project in pattern['projects']:
+      warnings[project][value] += pattern['projects'][project]
   return warnings
 
 
@@ -173,11 +172,11 @@
   """Returns list of HTML-formatted content for severity stats."""
 
   stats_header = ['Project']
-  for s in Severity.levels:
-    if total_by_severity[s.value]:
+  for severity in Severity.levels:
+    if total_by_severity[severity.value]:
       stats_header.append(
           '<span style=\'background-color:{}\'>{}</span>'.format(
-              s.color, s.column_header))
+              severity.color, severity.column_header))
   stats_header.append('TOTAL')
   return stats_header
 
@@ -200,15 +199,15 @@
 
   total_all_projects = 0
   stats_rows = []
-  for p in project_names:
-    if total_by_project[p]:
-      one_row = [p]
-      for s in Severity.levels:
-        if total_by_severity[s.value]:
-          one_row.append(warnings[p][s.value])
-      one_row.append(total_by_project[p])
+  for p_name in project_names:
+    if total_by_project[p_name]:
+      one_row = [p_name]
+      for severity in Severity.levels:
+        if total_by_severity[severity.value]:
+          one_row.append(warnings[p_name][severity.value])
+      one_row.append(total_by_project[p_name])
       stats_rows.append(one_row)
-      total_all_projects += total_by_project[p]
+      total_all_projects += total_by_project[p_name]
   return total_all_projects, stats_rows
 
 
@@ -226,10 +225,10 @@
 
   total_all_severities = 0
   one_row = ['<b>TOTAL</b>']
-  for s in Severity.levels:
-    if total_by_severity[s.value]:
-      one_row.append(total_by_severity[s.value])
-      total_all_severities += total_by_severity[s.value]
+  for severity in Severity.levels:
+    if total_by_severity[severity.value]:
+      one_row.append(total_by_severity[severity.value])
+      total_all_severities += total_by_severity[severity.value]
   one_row.append(total_all_projects)
   stats_rows.append(one_row)
   writer('<script>')
@@ -328,8 +327,8 @@
   for text in fixed_patterns:
     cur_row_class = 1 - cur_row_class
     # remove last '\n'
-    t = text[:-1] if text[-1] == '\n' else text
-    writer('<tr><td class="c' + str(cur_row_class) + '">' + t + '</td></tr>')
+    out_text = text[:-1] if text[-1] == '\n' else text
+    writer('<tr><td class="c' + str(cur_row_class) + '">' + out_text + '</td></tr>')
   writer('</table></div>')
   writer('</blockquote>')
 
@@ -339,10 +338,10 @@
   total = 0
   for pattern in warn_patterns:
     if pattern['severity'] == sev and pattern['members']:
-      n = len(pattern['members'])
-      total += n
+      num_members = len(pattern['members'])
+      total += num_members
       warning = kind + ': ' + (pattern['description'] or '?')
-      csvwriter.writerow([n, '', warning])
+      csvwriter.writerow([num_members, '', warning])
       # print number of warnings for each project, ordered by project name
       projects = sorted(pattern['projects'].keys())
       for project in projects:
@@ -355,8 +354,8 @@
   """Dump number of warnings in CSV format to writer."""
   sort_warnings(warn_patterns)
   total = 0
-  for s in Severity.levels:
-    total += write_severity(csvwriter, s, s.column_header, warn_patterns)
+  for severity in Severity.levels:
+    total += write_severity(csvwriter, severity, severity.column_header, warn_patterns)
   csvwriter.writerow([total, '', 'All warnings'])
 
 
@@ -379,35 +378,35 @@
     csvwriter.writerow(output)
 
 
-# Return s with escaped backslash and quotation characters.
-def escape_string(s):
-  return s.replace('\\', '\\\\').replace('"', '\\"')
+# Return line with escaped backslash and quotation characters.
+def escape_string(line):
+  return line.replace('\\', '\\\\').replace('"', '\\"')
 
 
-# Return s without trailing '\n' and escape the quotation characters.
-def strip_escape_string(s):
-  if not s:
-    return s
-  s = s[:-1] if s[-1] == '\n' else s
-  return escape_string(s)
+# Return line without trailing '\n' and escape the quotation characters.
+def strip_escape_string(line):
+  if not line:
+    return line
+  line = line[:-1] if line[-1] == '\n' else line
+  return escape_string(line)
 
 
 def emit_warning_array(name, writer, warn_patterns):
   writer('var warning_{} = ['.format(name))
-  for w in warn_patterns:
+  for pattern in warn_patterns:
     if name == 'severity':
-      writer('{},'.format(w[name].value))
+      writer('{},'.format(pattern[name].value))
     else:
-      writer('{},'.format(w[name]))
+      writer('{},'.format(pattern[name]))
   writer('];')
 
 
 def emit_warning_arrays(writer, warn_patterns):
   emit_warning_array('severity', writer, warn_patterns)
   writer('var warning_description = [')
-  for w in warn_patterns:
-    if w['members']:
-      writer('"{}",'.format(escape_string(w['description'])))
+  for pattern in warn_patterns:
+    if pattern['members']:
+      writer('"{}",'.format(escape_string(pattern['description'])))
     else:
       writer('"",')  # no such warning
   writer('];')
@@ -566,32 +565,32 @@
 # Emit a JavaScript const integer array.
 def emit_const_int_array(name, array, writer):
   writer('const ' + name + ' = [')
-  for n in array:
-    writer(str(n) + ',')
+  for item in array:
+    writer(str(item) + ',')
   writer('];')
 
 
 # Emit a JavaScript const string array.
 def emit_const_string_array(name, array, writer):
   writer('const ' + name + ' = [')
-  for s in array:
-    writer('"' + strip_escape_string(s) + '",')
+  for item in array:
+    writer('"' + strip_escape_string(item) + '",')
   writer('];')
 
 
 # Emit a JavaScript const string array for HTML.
 def emit_const_html_string_array(name, array, writer):
   writer('const ' + name + ' = [')
-  for s in array:
-    writer('"' + html.escape(strip_escape_string(s)) + '",')
+  for item in array:
+    writer('"' + html.escape(strip_escape_string(item)) + '",')
   writer('];')
 
 
 # Emit a JavaScript const object array.
 def emit_const_object_array(name, array, writer):
   writer('const ' + name + ' = [')
-  for x in array:
-    writer(str(x) + ',')
+  for item in array:
+    writer(str(item) + ',')
   writer('];')
 
 
@@ -671,8 +670,8 @@
                warning_links, warning_records, header_str):
   """Write warnings html file."""
   if html_path:
-    with open(html_path, 'w') as f:
-      dump_html(flags, f, warning_messages, warning_links, warning_records,
+    with open(html_path, 'w') as outf:
+      dump_html(flags, outf, warning_messages, warning_links, warning_records,
                 header_str, warn_patterns, project_names)
 
 
@@ -680,12 +679,12 @@
                   warning_records, header_str, project_names):
   """Write warnings csv file."""
   if flags.csvpath:
-    with open(flags.csvpath, 'w') as f:
-      dump_csv(csv.writer(f, lineterminator='\n'), warn_patterns)
+    with open(flags.csvpath, 'w') as outf:
+      dump_csv(csv.writer(outf, lineterminator='\n'), warn_patterns)
 
   if flags.csvwithdescription:
-    with open(flags.csvwithdescription, 'w') as f:
-      dump_csv_with_description(csv.writer(f, lineterminator='\n'),
+    with open(flags.csvwithdescription, 'w') as outf:
+      dump_csv_with_description(csv.writer(outf, lineterminator='\n'),
                                 warning_records, warning_messages,
                                 warn_patterns, project_names)