Python:避免 NumPy 的 unittest.py 与本地 unittest.py 的冲突

Question

有没有人遇到过这样的情况，他们将自己代码的单元测试写到一个名为unittest.py的文件中，发现它与NumPy的unittest.py模块冲突？换句话说，如果我将其写入本地目录中的 unittest.py:

if __name__ == "__main__":
    print "pre-import"
    #import numpy
    print "post-import"

然后(这里没有惊喜):

% python unittest.py
pre-import
post-import

但如果我这样做:

if __name__ == "__main__":
    print "pre-import"
    import numpy
    print "post-import"

我得到:

% python unittest.py
pre-import
Traceback (most recent call last):
  File "unittest.py", line 3, in <module>
    import numpy
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/__init__.py", line 137, in <module>
    import add_newdocs
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/add_newdocs.py", line 9, in <module>
    from numpy.lib import add_newdoc
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/lib/__init__.py", line 4, in <module>
    from type_check import *
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/lib/type_check.py", line 8, in <module>
    import numpy.core.numeric as _nx
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/core/__init__.py", line 40, in <module>
    from numpy.testing import Tester
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/testing/__init__.py", line 8, in <module>
    from unittest import TestCase
ImportError: cannot import name TestCase

随后，iPython 加载失败:

% ipython
WARNING: IPython History requires SQLite, your history will not be saved
Traceback (most recent call last):
  File "/home/jbbrown/local_bin/python/bin/ipython", line 7, in <module>
    launch_new_instance()
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/frontend/terminal/ipapp.py", line 402, in launch_new_instance
    app.initialize()
  File "<string>", line 2, in initialize
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/config/application.py", line 84, in catch_config_error
    return method(app, *args, **kwargs)
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/frontend/terminal/ipapp.py", line 312, in initialize
    self.init_shell()
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/frontend/terminal/ipapp.py", line 332, in init_shell
    ipython_dir=self.ipython_dir)
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/config/configurable.py", line 318, in instance
    inst = cls(*args, **kwargs)
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/frontend/terminal/interactiveshell.py", line 183, in __init__
    user_module=user_module, custom_exceptions=custom_exceptions
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 478, in __init__
    self.init_reload_doctest()
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 662, in init_reload_doctest
    doctest_reload()
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/IPython/utils/doctestreload.py", line 72, in doctest_reload
    import doctest
  File "/home/jbbrown/local_bin/python/lib/python2.7/doctest.py", line 2118, in <module>
    class DocTestCase(unittest.TestCase):
AttributeError: 'module' object has no attribute 'TestCase'

If you suspect this is an IPython bug, please report it at:
    https://github.com/ipython/ipython/issues
or send an email to the mailing list at ipython-dev@scipy.org

You can print a more detailed traceback right now with "%tb", or use "%debug"
to interactively debug it.

Extra-detailed tracebacks for bug-reporting purposes can be enabled via:
    c.Application.verbose_crash=True

有趣的是，如果我将 import 语句移到 "if __name__" 套件之外，例如，

print "pre-import"
import numpy
print "post-import"
if __name__ == "__main__":
    pass

我得到:

% python unittest.py
pre-import
pre-import
post-import
Traceback (most recent call last):
  File "unittest.py", line 2, in <module>
    import numpy
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/__init__.py", line 137, in <module>
    import add_newdocs
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/add_newdocs.py", line 9, in <module>
    from numpy.lib import add_newdoc
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/lib/__init__.py", line 4, in <module>
    from type_check import *
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/lib/type_check.py", line 8, in <module>
    import numpy.core.numeric as _nx
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/core/__init__.py", line 40, in <module>
    from numpy.testing import Tester
  File "/home/jbbrown/local_bin/python/lib/python2.7/site-packages/numpy/testing/__init__.py", line 8, in <module>
    from unittest import TestCase
ImportError: cannot import name TestCase

当然，更改包含我的单元测试的文件的名称并避免这种情况是微不足道的，但我想知道是否有其他人遇到过这种情况并想到了一种不包括重命名他们的单元测试文件的优雅解决方法？

Answer 1

您可以切换到absolute imports默认情况下，在 2.7 以上的 Python 版本上:

from __future__ import absolute_import

if __name__ == "__main__":
    print "pre-import"
    import numpy
    print "post-import"