How exactly (and why) can I access all of NumPy through numpy.random?

Question

I was poking through what is available in numpy.random after importing

from numpy import random

with dir(random), and noticed that there was a variable np in scope, which appears equivalent to the top-level module, for example

In[1]: from numpy import random

In[2]: random.np.fft.fft2
Out[2]: <function numpy.fft.fftpack.fft2>

In[3]: random.np.random.np.fft.np # not the same for fft

AttributeErrorTraceback (most recent call last)
<ipython-input-78-a64e04c36c80> in <module>()
----> 1 random.np.random.np.fft.np

AttributeError: module 'numpy.fft' has no attribute 'np'

This seems a bit strange to me... or at least not something I've seen before in other Python modules. It looks like I can access everything I could with import numpy as np through the np variable in random.

I wanted to see how it was available to the submodule, so I looked in numpy/random/__init__.py in the source code, and didn't see how it is made available. I also looked in numpy/random/info.py at __all__, but can't find how it is exposed to the module.

How is the top level module made available to numpy.random, and is there any motivation for having it available?

Stephen Rauch · Accepted Answer · 2017-03-06 06:41:52Z

2

So in numpy/random/mtrand/mtrand.pyx line 146 we find:

import numpy as np

Thus placing the symbol into the module's namespace. Which, this being python, you can access. I would imagine that this line is present for the same reason we litter it all over our modules, namely this module needs access to numpy functionality.

And backing up one level we find in /numpy/random/__init__.py line 99:

from .mtrand import *

Which closes the circle and gets us access to np via the numpy.random module.

edited Mar 6, 2017 at 6:41

answered Mar 6, 2017 at 3:34

Stephen Rauch♦

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1 Comment

Eric Hansen Over a year ago

You found it! More straightforward than I was making it out to be, thanks!

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