In Python the definition of package is very simple. Like Java the hierarchical structure and the directory structure are the same. But you have to have __init__.py in a package. I will explain the __init__.py file with the example below:
package_x/
|-- __init__.py
|-- subPackage_a/
|------ __init__.py
|------ module_m1.py
|-- subPackage_b/
|------ __init__.py
|------ module_n1.py
|------ module_n2.py
|------ module_n3.py
__init__.py can be empty, as long as it exists. It indicates that the directory should be regarded as a package. Of course, __init__.py can also set the appropriate content.
If we add a function in module_n1:
def function_X():
print "function_X in module_n1"
return
After running:
>>>from package_x.subPackage_b.module_n1 import function_X
>>>function_X()
function_X in module_n1
Then we followed the hierarchy package and called module_n1 the function. We can use __init__.py in subPackage_b like this:
__all__ = ['module_n2', 'module_n3']
After running:
>>>from package_x.subPackage_b import *
>>>module_n1.function_X()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named module_n1
Hence using * importing, module package is subject to __init__.py content.