使用包的别名时，为什么从包导入无效? [英] Why is importing from a package invalid when the aliased name of package is used?

问题描述

为了更加清楚，请考虑一个小例子:

To make it more clear, consider a numpy example :

import numpy as np
from numpy import array

这按预期工作.但是呢:

This works as expected. But what about this:

from np import array

输出为:

Traceback (most recent call last)
  <ipython-input-21-d5c81fa93e5f> in <module>()
    ----> 1 from np import array
ModuleNotFoundError: No module named 'np'

一旦将导入的模块numpy的别名设置为np，我是否只能使用np导入其他内容?

Once I have set the alias of the imported module numpy as np, shouldn't I be able to import something else using np only?

此外，两者的id()是相同的-numpy和np都指相同的事物.

Also, the id() of both is the same -- both numpy and np refer to the same thing.

推荐答案

即使将模块导入为np，模块名称仍为numpy.

The module name is still numpy, even after you import the module as np.

import … as …语法的主要作用是:

np = internal_import_module('numpy')

因此，np只是用来引用numpy模块的本地名称.如果查看模块名称np，您会发现它仍然是'numpy':

So the np is just the local name that get used to refer to the numpy module. If you look at the module name of np, you can see that it’s still 'numpy':

>>> import numpy as np
>>> np.__name__
'numpy'

现在，在评估另一个import语句时，根本不使用模块的本地名称.所以您的from numpy import array基本上就是这样:

Now, the local name of a module is not being used at all when another import statement is being evaluated. So your from numpy import array is basically just this:

array = internal_import_module('numpy').array

此处array还是numpy模块内部array成员的本地名称.但是，它不是np模块内部的成员，因为根本就没有该名称的模块.

Here array is again just a local name for the array member inside of the numpy module. It is however not a member inside of the np module because there simply isn’t a module with that name.

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