Update app.py

app.py

@@ -199,10 +199,11 @@ def merge_lines(doc1, doc2, doc3, doc4):
     merged_lines = []
 
     with open("merged_lines.txt", "w") as f:
-        for lines in zip(*[open(doc) for doc in docs]):
-            merged_line = "\n".join(line.strip() for line in lines)
-            f.write(merged_line + "\n")
-            merged_lines.append(merged_line)
+        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)
 
     return merged_lines