diff --git a/materials.py b/materials.py
index 450de8c..8ba1f36 100644
--- a/materials.py
+++ b/materials.py
@@ -20,10 +20,10 @@ VERSION = """\
 EPILOG = """\
 """
 
-import os
-
-
-def list():
+def list_files():
+  """\
+  List all materials
+  """
   from os import listdir
 
   for data in listdir("./data"):
@@ -31,24 +31,29 @@ def list():
     if file_name != "INFO":
       print(file_name)
 
-
-def read(input, search_keys=None):
+def read(input_file, search_keys=None):
+  """\
+  Read json file
+  """
+  import os
   import json
   from pprint import pprint
 
-  def find_values(id, json_repr):
+  def find_values(key, json_repr):
     results = []
 
     def _decode_dict(a_dict):
-      try: results.append(a_dict[id])
-      except KeyError: pass
+      try:
+        results.append(a_dict[key])
+      except KeyError:
+        pass
       return a_dict
 
     json.loads(json_repr, object_hook=_decode_dict)  # return value ignored
     return results
 
   try:
-    with open(os.path.join('data', input + '.json')) as data_file:
+    with open(os.path.join('data', input_file + '.json')) as data_file:
       if search_keys is not None:
         data = data_file.read()
         for search_key in search_keys:
@@ -76,7 +81,6 @@ def read(input, search_keys=None):
     sys.exit(2)
 
 
-
 def main():
   """\
   Main function
@@ -117,7 +121,7 @@ def main():
     print(args)
 
   if args.command == 'list':
-    list()
+    list_files()
 
   elif args.command == 'material':
     if args.const_collection: