diff --git a/kaldifeat/python/kaldifeat/__init__.py b/kaldifeat/python/kaldifeat/__init__.py
index d32c46c..92e7980 100644
--- a/kaldifeat/python/kaldifeat/__init__.py
+++ b/kaldifeat/python/kaldifeat/__init__.py
@@ -8,6 +8,8 @@ if torch.__version__.split("+")[0] != kaldifeat_torch_version.split("+")[0]:
         f"But you are using PyTorch {torch.__version__} to run it"
     )
 
+from pathlib import Path as _Path
+
 from _kaldifeat import (
     FbankOptions,
     FrameExtractionOptions,
@@ -15,6 +17,7 @@ from _kaldifeat import (
     MfccOptions,
     PlpOptions,
     SpectrogramOptions,
+    num_frames,
 )
 
 from .fbank import Fbank, OnlineFbank
@@ -24,7 +27,5 @@ from .online_feature import OnlineFeature
 from .plp import OnlinePlp, Plp
 from .spectrogram import Spectrogram
 
-from pathlib import Path as _Path
-
 cmake_prefix_path = _Path(__file__).parent / "share" / "cmake"
 del _Path