Should I use `import os.path` or `import os`?
coding-style, python, python-import
Solution
`os.path` works in a funny way. It looks like `os` should be a package with a submodule `path`, but in reality `os` is a normal module that does magic with `sys.modules` to inject `os.path`. Here's what happens:
When Python starts up, it loads a bunch of modules into `sys.modules`. They aren't bound to any names in your script, but you can access the already-created modules when you import them in some way.
- `sys.modules` is a dict in which modules are cached. When you import a module, if it already has been imported somewhere, it gets the instance stored in `sys.modules`.
`os` is among the modules that are loaded when Python starts up. It assigns its `path` attribute to an os-specific path module.
It injects `sys.modules['os.path'] = path` so that you're able to do "`import os.path`" as though it was a submodule.
I tend to think of `os.path` as a module I want to use rather than a thing in the `os` module, so even though it's not really a submodule of a package called `os`, I import it sort of like it is one and I always do `import os.path`. This is consistent with how `os.path` is documented.
Incidentally, this sort of structure leads to a lot of Python programmers' early confusion about modules and packages and code organization, I think. This is really for two reasons
If you think of `os` as a package and know that you can do `import os` and have access to the submodule `os.path`, you may be surprised later when you can't do `import twisted` and automatically access `twisted.spread` without importing it.
It is confusing that `os.name` is a normal thing, a string, and `os.path` is a module. I always structure my packages with empty `__init__.py` files so that at the same level I always have one type of thing: a module/package or other stuff. Several big Python projects take this approach, which tends to make more structured code.
Problem
According to the official documentation, `os.path` is a module. Thus, what is the preferred way of importing it? ``` # Should I always import it explicitly? import os.path ``` Or... ``` # Is importing os enough? import os ``` Please DON'T answer "importing `os` works for me". I know, it works for me too right now (as of Python 2.6). What I want to know is any official recommendation about this issue. So, if you answer this question, please post your references.