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

Question

其他人是否遇到过这样的情况：他们将代码的单元测试编写到名为unittest.py发现它和纽比的有冲突unittest.py模块？换句话说，如果我写信给unittest.py在本地目录中：

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

然后（这里没有意外）：

^{pr2}$

但如果我这么做了：

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无法加载：

% 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一点很简单，但我想知道是否有人遇到了这种情况，并想到了一种不包括重命名单元测试文件的优雅解决方案？在

Answer 1

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

from __future__ import absolute_import

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