Avoid repeated handler lookups.

Summary: it's more idiomatic and avoids the second lookup for matching path

Reviewed By: calebho

Differential Revision: D55931716

fbshipit-source-id: ee71b6817c4f77f27994d6f892ea0b732e9f12aa

iopath/common/file_io.py

@@ -964,9 +964,9 @@ def __get_path_handler(self, path: Union[str, os.PathLike]) -> PathHandler:
             handler (PathHandler)
         """
         path = os.fspath(path)  # pyre-ignore
-        for p in self._path_handlers.keys():
+        for p, handler in self._path_handlers.items():
             if path.startswith(p):
-                return self._path_handlers[p]
+                return handler
         return self._native_path_handler
 
     def __log_tmetry_keys(self, handler: PathHandler, kvs: Dict[str, VTYPE]) -> None: