Question

I am trying to organize some modules for my own use. I have something like this:

lib/   __init__.py   settings.py   foo/     __init__.py     someobject.py   bar/     __init__.py     somethingelse.py 

In lib/__init__.py, I want to define some classes to be used if I import lib. However, I can’t seem to figure it out without separating the classes into files, and import them in__init__.py.

Rather than say:

    lib/       __init__.py       settings.py       helperclass.py       foo/         __init__.py         someobject.py       bar/         __init__.py         somethingelse.py  from lib.settings import Values from lib.helperclass import Helper 

I want something like this:

    lib/       __init__.py  #Helper defined in this file       settings.py       foo/         __init__.py         someobject.py       bar/         __init__.py         somethingelse.py  from lib.settings import Values from lib import Helper 

Is it possible, or do I have to separate the class into another file?

EDIT

OK, if I import lib from another script, I can access the Helper class. How can I access the Helper class from settings.py?

The example here describes Intra-Package References. I quote ‘submodules often need to refer to each other’. In my case, the lib.settings.py needs the Helper and lib.foo.someobject need access to Helper, so where should I define the Helper class?

Answer 1

1. ‘lib/‘s parent directory must be in sys.path.

2. Your ‘lib/__init__.py‘ might look like this:

   from . import settings # or just 'import settings' on old Python versions class Helper(object):       pass 

Then the following example should work:

from lib.settings import Values from lib import Helper 

Answer to the edited version of the question:

__init__.py defines how your package looks from outside. If you need to use Helper in settings.py then define Helper in a different file e.g., ‘lib/helper.py‘.

 . |   `-- import_submodule.py     `-- lib     |-- __init__.py     |-- foo     |   |-- __init__.py     |   `-- someobject.py     |-- helper.py     `-- settings.py  2 directories, 6 files 

The command:

$ python import_submodule.py 

Output:

settings helper Helper in lib.settings someobject Helper in lib.foo.someobject  # ./import_submodule.py import fnmatch, os from lib.settings import Values from lib import Helper  print for root, dirs, files in os.walk('.'):     for f in fnmatch.filter(files, '*.py'):         print '# %s/%s' % (os.path.basename(root), f)         print open(os.path.join(root, f)).read()         print   # lib/helper.py print 'helper' class Helper(object):     def __init__(self, module_name):         print 'Helper in', module_name   # lib/settings.py print 'settings' import helper  class Values(object):     pass  helper.Helper(__name__)   # lib/__init__.py #from __future__ import absolute_import import settings, foo.someobject, helper  Helper = helper.Helper   # foo/someobject.py print 'someobject' from .. import helper  helper.Helper(__name__)   # foo/__init__.py import someobject