MNT: imporve importing time by lazy importing Tester

hmaarrfk · hmaarrfk · commit 9ed23a348d13 · 2019-08-17T17:42:49.000-04:00
diff --git a/numpy/__init__.py b/numpy/__init__.py
@@ -166,6 +166,9 @@
     # now that numpy modules are imported, can initialize limits
     core.getlimits._register_known_types()
 
+    __all__.extend(['bool', 'int', 'float', 'complex', 'object', 'unicode',
+                    'str'])
+
     __all__.extend(['__version__', 'show_config'])
     __all__.extend(core.__all__)
     __all__.extend(_mat.__all__)
@@ -182,9 +185,35 @@
     oldnumeric = 'removed'
     numarray = 'removed'
 
-    # We don't actually use this ourselves anymore, but I'm not 100% sure that
-    # no-one else in the world is using it (though I hope not)
-    from .testing import Tester
+    if sys.version_info[:2] >= (3, 7):
+        # Importing Tester requires importing all of UnitTest which is not a
+        # cheap import Since it is mainly used in test suits, we lazy import it
+        # here to save on the order of 10 ms of import time for most users
+        #
+        # The previous way Tester was imported also had a side effect of adding
+        # the full `numpy.testing` namespace
+        #
+        # module level getattr is only supported in 3.7 onwards
+        # https://www.python.org/dev/peps/pep-0562/
+        def __getattr__(attr):
+            if attr == 'testing':
+                import numpy.testing as testing
+                return testing
+            elif attr == 'Tester':
+                from .testing import Tester
+                return Tester
+            else:
+                raise AttributeError(
+                    "module %s has no attribute $s".format(__name__, attr))
+
+
+        def __dir__():
+            return __all__ + ['Tester', 'testing']
+
+    else:
+        # We don't actually use this ourselves anymore, but I'm not 100% sure that
+        # no-one else in the world is using it (though I hope not)
+        from .testing import Tester
 
     # Pytest testing
     from numpy._pytesttester import PytestTester
diff --git a/numpy/tests/test_public_api.py b/numpy/tests/test_public_api.py
@@ -1,6 +1,7 @@
 from __future__ import division, absolute_import, print_function
 
 import sys
+import subprocess
 
 import numpy as np
 import pytest
@@ -69,6 +70,28 @@ def test_numpy_namespace():
     assert bad_results == whitelist
 
 
+@pytest.mark.parametrize('name', ['testing', 'Tester'])
+def test_import_lazy_import(name):
+    """Make sure we can actually the the modules we lazy load.
+
+    While not exported as part of the public API, it was accessible.  With the
+    use of __getattr__ and __dir__, this isn't always true It can happen that
+    an infinite recursion may happen.
+
+    This is the only way I found that would force the failure to appear on the
+    badly implemented code.
+
+    We also test for the presence of the lazily imported modules in dir
+
+    """
+    exe = (sys.executable, '-c', "import numpy; numpy." + name)
+    result = subprocess.check_output(exe)
+    assert not result
+
+    # Make sure they are still in the __dir__
+    assert name in dir(np)
+
+
 def test_numpy_linalg():
     bad_results = check_dir(np.linalg)
     assert bad_results == {}
