Question

I thought about this for a while and can’t think of a better title, sorry.

I’m new’ish to Python, and (like many other’s it seems) I just can’t get my head around import.

I think I understand ‘modules’ and ‘packages’, classes and attributes and all that. It’s one specific behavior I need clarified.

Say I have a file, foo.py. It has one line it:

x = 1

If, in another file, I `import foo”, I can reference x. And, wonderfully, in another file I can import foo and now those two files can share x. Leaving classes out of the discussion for simplicity, I believe this is the pythonic way to share attributes between files.

Here’s the question: Is is fair to say, when I import foo, that foo.py itself is, (for lack of a better metaphor), secretly instantiated by the interpreter?

I realize if I define a class in a module, it follow traditional rules and only become instantiated if I explicitly do so. But, the python interpreter (via the import statement) instantiating an instance of my module in the global namespace is the only way to explain the attribute sharing behavior.

Is this true? Semi-true? Or am I wandering with the Sleestaks in the Land of the Lost?

Answer 1

The import creates an instance of a “module” object. It is worth knowing that this is created only the first time the module is imported. The following times it is imported you are getting a reference to the original. You can create your own module objects on the fly with a bit of instrospection.

import glob  # Import any python module
moduleType = type(glob)

onTheFly = moduleType("OnTheFly", "Docstring for this module")

Although there isn’t much benefit to creating these.