testapp/
├── __init__.py
├── api
│   ├── __init__.py
│   └── utils.py
└── utils.py

from testapp import utils

print "a", utils

from testapp.api.utils import x

print "b", utils

x = 1

$ export PYTHONPATH=$PYTHONPATH:.
$ python -c "import testapp.api"
a <module 'testapp.utils' from 'testapp/utils.pyc'>
b <module 'testapp.api.utils' from 'testapp/api/utils.pyc'>

>>> from os.path import abspath
>>> path
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'path' is not defined

spam/
    __init__.py
    foo.py
    bar.py

from .foo import Foo
from .bar import Bar

>>> import spam
>>> spam.foo
<module 'spam.foo' from '/tmp/imports/spam/foo.py'>
>>> spam.bar
<module 'spam.bar' from '/tmp/imports/spam/bar.py'>