How to import custom python package by name

问题

I have created a folder named "custom_module" and I have the __init__.py inside the folder which contains:

__all__ = [
        'Submodule1',
        'Submodule2'
]

From what documentation I read I should be able to call import custom_module and get access to the package, however this isn't happening. How can I make python recognize my package? I am using python 3.2

Update: The package is not located in the python folder. How does the python environment find it, so I can successfully import it by name.

回答1:

sys.path holds the Python search path. Before trying to import your modules and packages, set it to include your path:

import sys
sys.path.insert(0, 'your_path_here')
import custom_module

More detail in the Python docs and in this question

回答2:

There are two distinct concepts you are confusing: packages and modules.

A module is what you think it is: a Python script containing classes, variables, whatever. You import it by its filename, and can then access the variables in its namespace.

A package is a collection of modules which are grouped together inside a folder. If the folder contains a file called __init__.py, Python will allow you to import the entire folder as if it were a module. This will run the code in __init__, but will not necessarily import all of the modules in the folder. (This is a deliberate design choice: packages are often very large, and importing all of the modules could take a very long time.)

The only things which are exported (as package.thing) by default are the variables defined inside __init__. If you want submodule to be available as package.submodule, you need to import it inside __init__.

__all__ is a related concept. In brief, it defines what is imported when you do from package import *, because it's not easy for Python to work out what that should be otherwise. You don't in general need it.

来源：https://stackoverflow.com/questions/12475678/how-to-import-custom-python-package-by-name