Python Revision - Section VI - Modules and Packages

Modules

In order to create a new module, we’ve just to create a new .py file with the module name and then import it using the Python file name using the import command.

import foo

Packages

Packages are name-spaces which contain multiple packages and modules themselves. They are simply directories in which must contain a special file called __init__.py that can be empty and indicates that the directory contains a Python package.

If we create a directory called foo, which marks the package name, we can then create a module inside that package called bar and add the __init__.py inside the foo directory.

To use the module bar, we can import it in two ways:

import foo.bar

or

from foo import bar

In the __init__.py file, we can define which module the package will export and which module we will keep internal by overriding the __all__ variable like this:

__all__=["bar"]

The __name__ == '__main__' verification

When we create a new module we can use it imported in other modules but we also would want to use it as a script. To make this differentiation we need to check if __name__ == '__main__'. Because if it’s true, that’s because the module was called directly, as a script and if it’s not, the module was imported. So, it’s pretty usual that in a module we have this kind of implementation:

def func1():
    pass

def func2():
    pass

if __name__ == '__main__':
    func1()
    func2()

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