fix calc_stats filter usage

calc_stats.py

@@ -90,15 +90,15 @@ def main():
         data = read_csv(sys.stdin)
     elif len(sys.argv) > 2:
         print_usage_and_exit()
-
-    data_path = Path(sys.argv[1])
-    if not data_path.exists():
-        print('Path: {data_path} does not exists')
-        sys.exit(1)
-    
-    if data_path.is_file():
-        with open(data_path, 'r') as data_file:
-            data = read_csv(data_file)
+    else:
+        data_path = Path(sys.argv[1])
+        if not data_path.exists():
+            print('Path: {data_path} does not exists')
+            sys.exit(1)
+
+        if data_path.is_file():
+            with open(data_path, 'r') as data_file:
+                data = read_csv(data_file)
 
     stats = calc_stats(data)
     print(yaml.safe_dump(stats))