a better handling of optional import.

examples/A3C-Gym/simulator.py

@@ -12,6 +12,7 @@ from collections import defaultdict
 
 import six
 from six.moves import queue
+import zmq
 
 from tensorpack.models.common import disable_layer_logging
 from tensorpack.callbacks import Callback
@@ -25,12 +26,6 @@ __all__ = ['SimulatorProcess', 'SimulatorMaster',
            'SimulatorProcessStateExchange', 'SimulatorProcessSharedWeight',
            'TransitionExperience', 'WeightSync']
 
-try:
-    import zmq
-except ImportError:
-    logger.warn_dependency('Simulator', 'zmq')
-    __all__ = []
-
 
 class TransitionExperience(object):
     """ A transition of state, or experience"""

tensorpack/RL/gymenv.py

@@ -5,18 +5,6 @@
 
 
 import time
-from ..utils import logger
-try:
-    import gym
-    # TODO
-    # gym.undo_logger_setup()
-    # https://github.com/openai/gym/pull/199
-    # not sure does it cause other problems
-    __all__ = ['GymEnv']
-except ImportError:
-    logger.warn_dependency('GymEnv', 'gym')
-    __all__ = []
-
 import threading
 
 from ..utils.fs import mkdir_p
@@ -24,6 +12,7 @@ from ..utils.stats import StatCounter
 from .envbase import RLEnvironment, DiscreteActionSpace
 
 
+__all__ = ['GymEnv']
 _ENV_LOCK = threading.Lock()
 
 
@@ -84,6 +73,17 @@ class GymEnv(RLEnvironment):
         return DiscreteActionSpace(spc.n)
 
 
+try:
+    import gym
+    # TODO
+    # gym.undo_logger_setup()
+    # https://github.com/openai/gym/pull/199
+    # not sure does it cause other problems
+except ImportError:
+    from ..utils.dependency import create_dummy_class
+    GymEnv = create_dummy_class('GymEnv', 'gym')    # noqa
+
+
 if __name__ == '__main__':
     env = GymEnv('Breakout-v0', viz=0.1)
     num = env.get_action_space().num_actions()

tensorpack/dataflow/dataset/bsds500.py

@@ -8,17 +8,11 @@ import glob
 import cv2
 import numpy as np
 
-from ...utils import logger, get_dataset_path
+from ...utils import get_dataset_path
 from ...utils.fs import download
 from ..base import RNGDataFlow
 
-try:
-    from scipy.io import loadmat
-    __all__ = ['BSDS500']
-except ImportError:
-    logger.warn_dependency('BSDS500', 'scipy.io')
-    __all__ = []
-
+__all__ = ['BSDS500']
 DATA_URL = "http://www.eecs.berkeley.edu/Research/Projects/CS/vision/grouping/BSR/BSR_bsds500.tgz"
 IMG_W, IMG_H = 481, 321
 
@@ -95,6 +89,12 @@ class BSDS500(RNGDataFlow):
             yield [self.data[k], self.label[k]]
 
 
+try:
+    from scipy.io import loadmat
+except ImportError:
+    from ...utils.dependency import create_dummy_class
+    BSDS500 = create_dummy_class('BSDS500', 'scipy.io')  # noqa
+
 if __name__ == '__main__':
     a = BSDS500('val')
     for k in a.get_data():

tensorpack/dataflow/dataset/svhn.py

@@ -9,12 +9,7 @@ import numpy as np
 from ...utils import logger, get_dataset_path
 from ..base import RNGDataFlow
 
-try:
-    import scipy.io
-    __all__ = ['SVHNDigit']
-except ImportError:
-    logger.warn_dependency('SVHNDigit', 'scipy.io')
-    __all__ = []
+__all__ = ['SVHNDigit']
 
 SVHN_URL = "http://ufldl.stanford.edu/housenumbers/"
 
@@ -73,6 +68,12 @@ class SVHNDigit(RNGDataFlow):
         return np.concatenate((a.X, b.X, c.X)).mean(axis=0)
 
 
+try:
+    import scipy.io
+except ImportError:
+    from ...utils.dependency import create_dummy_class
+    SVHNDigit = create_dummy_class('SVHNDigit', 'scipy.io')  # noqa
+
 if __name__ == '__main__':
     a = SVHNDigit('train')
     b = SVHNDigit.get_per_pixel_mean()

tensorpack/dataflow/dftools.py

@@ -15,13 +15,8 @@ from ..utils.concurrency import DIE
 from ..utils.serialize import dumps
 from ..utils.fs import mkdir_p
 
-__all__ = ['dump_dataset_images', 'dataflow_to_process_queue']
-try:
-    import lmdb
-except ImportError:
-    logger.warn_dependency("dump_dataflow_to_lmdb", 'lmdb')
-else:
-    __all__.extend(['dump_dataflow_to_lmdb'])
+__all__ = ['dump_dataset_images', 'dataflow_to_process_queue',
+           'dump_dataflow_to_lmdb']
 
 
 def dump_dataset_images(ds, dirname, max_count=None, index=0):
@@ -84,6 +79,13 @@ def dump_dataflow_to_lmdb(ds, lmdb_path):
             db.sync()
 
 
+try:
+    import lmdb
+except ImportError:
+    from ..utils.dependency import create_dummy_func
+    dump_dataflow_to_lmdb = create_dummy_func('dump_dataflow_to_lmdb', 'lmdb') # noqa
+
+
 def dataflow_to_process_queue(ds, size, nr_consumer):
     """
     Convert a DataFlow to a :class:`multiprocessing.Queue`.

tensorpack/dataflow/format.py

@@ -13,28 +13,8 @@ from ..utils.serialize import loads
 from ..utils.argtools import log_once
 from .base import RNGDataFlow
 
-try:
-    import h5py
-except ImportError:
-    logger.warn_dependency("HDF5Data", 'h5py')
-    __all__ = []
-else:
-    __all__ = ['HDF5Data']
-
-try:
-    import lmdb
-except ImportError:
-    logger.warn_dependency("LMDBData", 'lmdb')
-else:
-    __all__.extend(['LMDBData', 'LMDBDataDecoder', 'LMDBDataPoint', 'CaffeLMDB'])
-
-try:
-    import sklearn.datasets
-except ImportError:
-    logger.warn_dependency('SVMLightData', 'sklearn')
-else:
-    __all__.extend(['SVMLightData'])
-
+__all__ = ['HDF5Data', 'LMDBData', 'LMDBDataDecoder', 'LMDBDataPoint',
+           'CaffeLMDB', 'SVMLightData']
 
 """
 Adapters for different data format.
@@ -214,3 +194,21 @@ class SVMLightData(RNGDataFlow):
             self.rng.shuffle(idxs)
         for id in idxs:
             yield [self.X[id, :], self.y[id]]
+
+
+from ..utils.dependency import create_dummy_class   # noqa
+try:
+    import h5py
+except ImportError:
+    HDF5Data = create_dummy_class('HDF5Data', 'h5py')   # noqa
+
+try:
+    import lmdb
+except ImportError:
+    for klass in ['LMDBData', 'LMDBDataDecoder', 'LMDBDataPoint', 'CaffeLMDB']:
+        globals()[klass] = create_dummy_class(klass, 'lmdb')
+
+try:
+    import sklearn.datasets
+except ImportError:
+    SVMLightData = create_dummy_class('SVMLightData', 'sklearn')   # noqa

tensorpack/dataflow/prefetch.py

@@ -8,6 +8,7 @@ import itertools
 from six.moves import range, zip
 import uuid
 import os
+import zmq
 
 from .base import ProxyDataFlow
 from ..utils.concurrency import (ensure_proc_terminate,
@@ -16,13 +17,7 @@ from ..utils.serialize import loads, dumps
 from ..utils import logger
 from ..utils.gpu import change_gpu
 
-__all__ = ['PrefetchData', 'BlockParallel']
-try:
-    import zmq
-except ImportError:
-    logger.warn_dependency('PrefetchDataZMQ', 'zmq')
-else:
-    __all__.extend(['PrefetchDataZMQ', 'PrefetchOnGPUs'])
+__all__ = ['PrefetchData', 'BlockParallel', 'PrefetchDataZMQ', 'PrefetchOnGPUs']
 
 
 class PrefetchProcess(mp.Process):

tensorpack/dataflow/tf_func.py

@@ -3,22 +3,14 @@
 # File: tf_func.py
 # Author: Yuxin Wu <ppwwyyxxc@gmail.com>
 
+import tensorflow as tf
 from .base import ProxyDataFlow
-from ..utils import logger
 
-try:
-    import tensorflow as tf
-except ImportError:
-    logger.warn_dependency('TFFuncMapper', 'tensorflow')
-    __all__ = []
-else:
-    __all__ = []
 
 """ This file was deprecated """
 
 
 class TFFuncMapper(ProxyDataFlow):
-
     def __init__(self, ds,
                  get_placeholders, symbf, apply_symbf_on_dp, device='/cpu:0'):
         """

tensorpack/predict/concurrency.py

@@ -9,21 +9,10 @@ from six.moves import queue, range
 
 from ..utils.concurrency import DIE, StoppableThread
 from ..tfutils.modelutils import describe_model
-from ..utils import logger
-
 from .base import OfflinePredictor, AsyncPredictorBase
 
-try:
-    if six.PY2:
-        from tornado.concurrent import Future
-    else:
-        from concurrent.futures import Future
-except ImportError:
-    logger.warn_dependency('MultiThreadAsyncPredictor', 'tornado.concurrent')
-    __all__ = ['MultiProcessPredictWorker', 'MultiProcessQueuePredictWorker']
-else:
-    __all__ = ['MultiProcessPredictWorker', 'MultiProcessQueuePredictWorker',
-               'MultiThreadAsyncPredictor']
+__all__ = ['MultiProcessPredictWorker', 'MultiProcessQueuePredictWorker',
+           'MultiThreadAsyncPredictor']
 
 
 class MultiProcessPredictWorker(multiprocessing.Process):
@@ -171,3 +160,13 @@ class MultiThreadAsyncPredictor(AsyncPredictorBase):
             f.add_done_callback(callback)
         self.input_queue.put((dp, f))
         return f
+
+
+try:
+    if six.PY2:
+        from tornado.concurrent import Future
+    else:
+        from concurrent.futures import Future
+except ImportError:
+    from ..utils.dependency import create_dummy_class
+    MultiThreadAsyncPredictor = create_dummy_class('MultiThreadAsyncPredictor', 'tornado.concurrent')  # noqa

tensorpack/utils/dependency.py

+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# File: dependency.py
+# Author: Yuxin Wu <ppwwyyxxc@gmail.com>
+
+
+""" Utilities to handle dependency """
+
+__all__ = ['create_dummy_func', 'create_dummy_class']
+
+
+def create_dummy_class(klass, dependency):
+    """
+    When a dependency of a class is not available, create a dummy class which throws ImportError when used.
+
+    Args:
+        klass (str): name of the class.
+        dependency (str): name of the dependency.
+
+    Returns:
+        class: a class object
+    """
+    class _Dummy(object):
+        def __init__(self, *args, **kwargs):
+            raise ImportError("Cannot import '{}', therefore '{}' is not available".format(dependency, klass))
+    return _Dummy
+
+
+def create_dummy_func(func, dependency):
+    """
+    When a dependency of a function is not available, create a dummy function which throws ImportError when used.
+
+    Args:
+        func (str): name of the function.
+        dependency (str): name of the dependency.
+
+    Returns:
+        function: a function object
+    """
+    def _dummy(*args, **kwargs):
+        raise ImportError("Cannot import '{}', therefore '{}' is not available".format(dependency, func))
+    return _dummy

tensorpack/utils/logger.py

@@ -11,8 +11,7 @@ from datetime import datetime
 from six.moves import input
 import sys
 
-__all__ = ['set_logger_dir', 'disable_logger', 'auto_set_dir',
-           'warn_dependency']
+__all__ = ['set_logger_dir', 'disable_logger', 'auto_set_dir']
 
 
 class _MyFormatter(logging.Formatter):
@@ -128,8 +127,3 @@ def auto_set_dir(action=None, overwrite=False):
         os.path.join('train_log',
                      basename[:basename.rfind('.')]),
         action=action)
-
-
-def warn_dependency(name, dependencies):
-    """ Print warning about an import failure due to missing dependencies. """
-    warn("Failed to import '{}', {} won't be available'".format(dependencies, name))  # noqa: F821