Update app.py

app.py

@@ -198,12 +198,12 @@ def merge_lines(doc1, doc2, doc3, doc4):
     docs = [doc1, doc2, doc3, doc4]
     merged_lines = []
 
-    with open("merged_lines.txt", "w") as f:
-        with [open(doc) for doc in docs] as handles:
-            for lines in zip(*handles):
-                merged_line = "".join(line.strip() for line in lines)
-                f.write(merged_line + "\n")
-                merged_lines.append(merged_line)
+    with open("merged_lines.txt", "w") as f, \
+            *map(open, docs) as handles:
+        for lines in zip(*handles):
+            merged_line = "".join(line.strip() for line in lines)
+            f.write(merged_line + "\n")
+            merged_lines.append(merged_line)
 
     return merged_lines