CODEWITHSUNDEEP
pythondatetimetimeimportpython-3.6
Stefan
Stefan

Reputation: 33

Can't shadow python time module with my own time module

I have a folder with three files:

time.py and datetime.py are identical:

def ticks_ms():
    return 5

When test.py looks like this:

import datetime as t
print(t.ticks_ms())

it prints 5. If I change it to:

import time as t
print(t.ticks_ms())

I get:

AttributeError: module 'time' has no attribute 'ticks_ms'

Why can I shadow the datetime module but not the time module?

Upvotes: 0

Views: 223

Answers (1)

Dimitris Fasarakis Hilliard
Dimitris Fasarakis Hilliard

Reputation: 160437

Why can I shadow the datetime module but not the time module?

Because Python will first search for built-in modules (implemented in C) before searching for normal .py files (in various locations, starting from your cwd, see the contents of sys.path).

You can see this by inspecting sys.meta_path which contains finders that are queried when an import for a module occurs (a module which hasn't been found in sys.modules):

>>> sys.meta_path
[<class '_frozen_importlib.BuiltinImporter'>, 
 <class '_frozen_importlib.FrozenImporter'>, 
 <class '_frozen_importlib_external.PathFinder'>]

First in this list is BuiltinImporter which, as it's name implies, handles the finding of built-in modules.

The time module is built-in (see sys.builtin_module_names for a list of these):

>>> time
<module 'time' (built-in)>

and is found before a search for your time.py is performed. While datetime.py isn't:

>>> datetime
<module 'datetime' from '/home/jim/anaconda3/lib/python3.6/datetime.py'>

and so the datetime.py in your current working dir masks it (PathFinder finds datetime.py by looking at the entries listed in sys.path).

Yes, you can re-order the finders in sys.meta_path and put the PathFinder first thereby resulting in time.py getting found but, please don't do that (unless you're just experimenting :-).

Upvotes: 2

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