Reduce import time by lazily importing slow modules.

CHANGELOG.md

@@ -12,7 +12,7 @@
 - Improve TileSource class repr ([#765](../../pull/765))
 - Improve frame slider response with base quads ([#771](../../pull/771))
 - Default to nearest-neighbor scaling in lossless image conversion ([#772](../../pull/772))
-- Improve the import time ([#775](../../pull/775))
+- Improve the import time ([#775](../../pull/775), [#777](../../pull/777))
 
 ### Bug Fixes
 - The tile iterator could return excess tiles with overlap ([#773](../../pull/773))

sources/bioformats/large_image_source_bioformats/__init__.py

@@ -28,8 +28,6 @@
 import threading
 import types
 
-import bioformats
-import javabridge
 import numpy
 from pkg_resources import DistributionNotFound, get_distribution
 
@@ -46,6 +44,9 @@
     # package is not installed
     pass
 
+bioformats = None
+# import javabridge
+javabridge = None
 
 _javabridgeStarted = None
 _openImages = []
@@ -100,6 +101,14 @@ def _startJavabridge(logger):
     global _javabridgeStarted
 
     if _javabridgeStarted is None:
+        # Only import these when first asked.  They are slow to import.
+        global bioformats
+        global javabridge
+        if bioformats is None:
+            import bioformats
+        if javabridge is None:
+            import javabridge
+
         # We need something to wake up at exit and shut things down
         monitor = threading.Thread(target=_monitor_thread)
         monitor.daemon = True
@@ -119,7 +128,8 @@ def _startJavabridge(logger):
 def _stopJavabridge(*args, **kwargs):
     global _javabridgeStarted
 
-    javabridge.kill_vm()
+    if javabridge is not None:
+        javabridge.kill_vm()
     _javabridgeStarted = None
 
 

sources/nd2/large_image_source_nd2/__init__.py

@@ -21,14 +21,7 @@
 import types
 import warnings
 
-# Work around an issue in the PIMS package (can be removed once pims is
-# released for Python 3.10).  This must be before improt nd2reader.
-if True:
-    import collections.abc
-    collections.Iterable = collections.abc.Iterable
-
 import cachetools
-import nd2reader
 import numpy
 from pkg_resources import DistributionNotFound, get_distribution
 
@@ -37,14 +30,30 @@
 from large_image.exceptions import TileSourceError, TileSourceFileNotFoundError
 from large_image.tilesource import FileTileSource
 
+nd2reader = None
+
 try:
     __version__ = get_distribution(__name__).version
 except DistributionNotFound:
     # package is not installed
     pass
 
 
-warnings.filterwarnings('ignore', category=UserWarning, module='nd2reader')
+def _lazyImport():
+    """
+    Import the nd2reader module.  This is done when needed rather than in the
+    module initialization because it is slow.
+    """
+    global nd2reader
+
+    if nd2reader is None:
+        # Work around an issue in the PIMS package (can be removed once pims is
+        # released for Python 3.10).  This must be before import nd2reader.
+        if True:
+            import collections.abc
+            collections.Iterable = collections.abc.Iterable
+        import nd2reader
+        warnings.filterwarnings('ignore', category=UserWarning, module='nd2reader')
 
 
 class ND2FileTileSource(FileTileSource, metaclass=LruCacheMetaclass):
@@ -82,6 +91,7 @@ def __init__(self, path, **kwargs):
 
         self._pixelInfo = {}
 
+        _lazyImport()
         try:
             self._nd2 = nd2reader.ND2Reader(self._largeImagePath)
         except (UnicodeDecodeError,