diff --git a/4-1.py b/4-1.py
index c3e1221..bf5cd2e 100644
--- a/4-1.py
+++ b/4-1.py
@@ -114,13 +114,13 @@ def parse_goldfile_line(goldfile_line):
     GOLDFILE_PATTERN = '^(.+),(.+)'
     match = re.search(GOLDFILE_PATTERN, goldfile_line)
     if match is None:
-        print(f'Invalid goldfile line: {goldfile_line}')
+        print('Invalid goldfile line: {0}'.format(goldfile_line))
         return (goldfile_line, -1)
     elif match.group(1) == '"idAmazon"':
-        print(f'Header datafile line: {goldfile_line}')
+        print('Header datafile line: {0}'.format(goldfile_line))
         return (goldfile_line, 0)
     else:
-        key = f'{match.group(1)} {match.group(2)}'
+        key = '{0} {1}'.format(match.group(1), match.group(2))
         return ((key, 'gold'), 1)
 
 # 9. 使用广播变量提高效率