Delete modules to clean namespace?

Question

I am working on a pretty huge Python package. Inside several modules, different programmers import other modules to do calculations. For the sake of this discussion, let's stick to numpy.

Common practice, when importing modules is defining an alias for easier programming, so let's say in a module foo.py there is a line doing

import numpy as np

So there will be a foo.np namespace. I also found out, that by deleting the reference to np inside foo.py by doing

del np

at the end of the module seems to clear the namespace as well.

As a maintainer of a huge package, I like this way of keeping the namespace clean but I wonder if this is good programming practice or if there are problems arising especially if my package has a module bar.py in the same level as foo.py which also uses the same external numpy module? If yes, is there a simple and better way to keep the namespaces of foo and bar clean or is this housekeeping of namespaces itself a bad idea?

Answer 1

Here is a simple example:

foo.py:

import numpy as np

def foo(x):
    """Return 2D square array of zeros."""
    return np.zeros((x, x))

del np

bar.py:

import numpy as np

def bar():
    """Return 3x3 square array."""
    return np.arange(9).reshape(3, 3)

main.py:

from bar import bar
from foo import foo

print bar()

print foo(3)

And here are the outputs:

[[0 1 2]
 [3 4 5]
 [6 7 8]]

Traceback (most recent call last):
  File "/Users/jonrsharpe/Documents/main.py", line 6, in <module>
    print foo(3)
  File "/Users/jonrsharpe/Documents/foo.py", line 5, in foo
    return np.zeros((x, x))
NameError: global name 'np' is not defined

So clearly this has not affected bar.py (which you should expect - del removes that reference, but doesn't affect the underlying object) but has broken the functionality imported from foo.py, as np is no longer accessible to the objects defined in that file.

---

is this housekeeping of namespaces itself a bad idea?

I'm not sure what you see as the benefits of it. Removing names from the namespace of a module you've finished using is not going to save very much (if any) space, and the underlying imported module (numpy, in this case) will still be in sys.modules.