enhancement (#803)

compression/huffman.py

@@ -29,12 +29,7 @@ def parse_file(file_path):
             if not c:
                 break
             chars[c] = chars[c] + 1 if c in chars.keys() else 1
-    letters = []
-    for char, freq in chars.items():
-        letter = Letter(char, freq)
-        letters.append(letter)
-    letters.sort(key=lambda l: l.freq)
-    return letters
+    return sorted([Letter(c, f) for c, f in chars.items()], key=lambda l: l.freq)
 
 def build_tree(letters):
     """