Making imported modules or imported methods in single file module private

Question

When I have a single file module relying on a 3rd party module or method from a 3rd party module which is imported in the single file module, then I have access to the 3rd party module or method when I import the single file module. I want to prevent that, my suggestion was to import the 3rd party module or method and renaming them with an underscore in front. Would that be a good idea, what other options do I have.

Example 1:

# this is a single file module called DemoModule.py
import numpy as np


def calculate_something():
    x = np.cos(0)

    return x

Now when I import DemoModule I do not only have access to calculate_something, but I also have access to everything numpy has to offer as well. Would this be a good way to avoid that situation:

# this is a single file module called DemoModule.py
import numpy as _np


def calculate_something():
    x = _np.cos(0)

    return x

Example 2:

# this is a single file module called DemoModule.py

from numpy import cos


def calculate_something():
    x = cos(0)

    return x

Now when I import DemoModule I do not only have access to calculate_something, but I also have access to cos. Would this be a good way to avoid that situation:

# this is a single file module called DemoModule.py

from numpy import cos as _cos


def calculate_something():
    x = _cos(0)

    return x

Edit:

A run from the command line

In[2]: import DemoModule
In[3]: DemoModule.np.cos(1)
Out[3]: 0.54030230586813977

Answer 1

First the usual disclaimer: Python has no concept of enforced "privacy" - the single leading underscore is only a naming convention saying "let's pretend you don't know this exists" (I assume you know this already but better to make things clear right from the start).

And the canonical answer is : define the __all__ attribute of your module with the names you want to publicly expose - every other name in the module should then be considered by users as "private". You can double this with a single-leading-underscore (import foo as _foo) if you really want to make the point clear but that's perhaps a bit over the top.