Python: modules and packaging - why isn't __init__.py file executed before __main__.py?

Question

I have a python program that is entirely contained in a directory with the following structure:

myprog/
├── __init__.py
├── __main__.py
├── moduleone.py
└── moduletwo.py

I would like to be able to package this and distribute it so that another developer can do pip install -e /path/to/git/clone/of/myprog and can then import myprog in his own programs and do cool stuff with it.

I would also like to be able to run myprog at the command line as follows:

PROMPT> python myprog

When I do this, I expect python to execute the __main__.py module, which it does. However, this module makes references to some functions that are declared in __init__.py and which need to be available both when the program is run at the command line and when it is imported by another program. However, I'm getting the following error:

NameError: name 'function_you_referenced_from_init_file' is not defined

Do I have to import these functions into __main__.py somehow?

I tried a simple example as follows:

PROMPT> cat myprog/__init__.py
def init_myprog():
    print 'running __init__.init_myprog()'

PROMPT> cat myprog/__main__.py
import myprog
print 'hi from __main__.py'
myprog.init_myprog()

PROMPT> ls -l myprog
total 16
-rw-r--r--  1 iit    63B Aug 30 11:40 __init__.py
-rw-r--r--  1 iit    64B Aug 30 12:11 __main__.py

PROMPT> python myprog
Traceback (most recent call last):
  File "/usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/Users/jon/dev/myprog/__main__.py", line 1, in <module>
    import myprog
ImportError: No module named myprog

Answer 1

The __init__.py is only loaded when you are import the package. You are instead treating the directory as a script, by executing the directory.

You can still treat the package as a script, instead of the directory however. To both treat the directory as a package and as the main script, by using the -m switch:

python -m myprog