use optional import

Author: David Eigen

clarifai/client/model.py

@@ -24,6 +24,7 @@
                                       MAX_RANGE_SIZE, MIN_CHUNK_SIZE, MIN_RANGE_SIZE,
                                       MODEL_EXPORT_TIMEOUT, RANGE_SIZE, TRAINABLE_MODEL_TYPES)
 from clarifai.errors import UserError
+from clarifai.runners.utils import video_utils
 from clarifai.urls.helper import ClarifaiUrlHelper
 from clarifai.utils.logging import logger
 from clarifai.utils.misc import BackoffIterator
@@ -1204,7 +1205,6 @@ def stream_by_video_file(self,
     # by getting the original start time ffprobe and either sending that to the model so it can adjust
     # with the ts of the first frame (too fragile to do all of this adjustment in the client input stream)
     # or by adjusting the timestamps in the output stream
-    from clarifai.runners.utils import video_utils
     stream = video_utils.convert_to_streamable(filepath)
 
     # TODO accumulate reads to fill the chunk size

clarifai/runners/utils/video_utils.py

@@ -3,10 +3,12 @@
 import tempfile
 import threading
 
-import av
 import requests
 
 from clarifai.runners.utils import stream_utils
+from clarifai.utils.misc import optional_import
+
+av = optional_import("av", pip_package="av")
 
 
 def stream_frames_from_url(url, download_ok=True):

clarifai/utils/misc.py

@@ -1,3 +1,4 @@
+import importlib
 import os
 import re
 import uuid
@@ -6,6 +7,29 @@
 from clarifai.errors import UserError
 
 
+def optional_import(module_name: str, pip_package: str = None):
+  """Import a module if it exists.
+     Otherwise, return an object that will raise an error when accessed.
+  """
+  try:
+    return importlib.import_module(module_name)
+  except ImportError:
+    return _MissingModule(module_name, pip_package=pip_package)
+
+
+class _MissingModule:
+  """Object that raises an error when accessed."""
+
+  def __init__(self, module_name, pip_package=None):
+    self.module_name = module_name
+    self.message = f"Module `{module_name}` is not installed."
+    if pip_package:
+      self.message += f" Please add `{pip_package}` to your requirements.txt file."
+
+  def __getattr__(self, name):
+    raise ImportError(self.message)
+
+
 class Chunker:
   """Split an input sequence into small chunks."""