Distutils - Where Am I going wrong?

Question

I wanted to learn how to create python packages, so I visited http://docs.python.org/distutils/index.html.

For this exercise I'm using Python 2.6.2 on Windows XP.

I followed along with the simple example and created a small test project:

person/

    setup.py

    person/
       __init__.py
       person.py

My person.py file is simple:

class Person(object):   
    def __init__(self, name="", age=0):
        self.name = name
        self.age = age

    def sound_off(self):
        print "%s %d" % (self.name, self.age)

And my setup.py file is:

from distutils.core import setup
setup(name='person',
    version='0.1',
    packages=['person'],
    )

I ran python setup.py sdist and it created MANIFEST, dist/ and build/. Next I ran python setup.py install and it installed it to my site packages directory.

I run the python console and can import the person module, but I cannot import the Person class.

>>>import person
>>>from person import Person
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name Person

I checked the files added to site-packages and checked the sys.path in the console, they seem ok. Why can't I import the Person class. Where did I go wrong?

Answer 1

person/
   __init__.py
   person.py

You've got a package called person, and a module inside it called person.person. You defined the class in that module, so to access it you'd have to say:

import person.person
p= person.person.Person('Tim', 42)

If you want to put members directly inside the package person, you'd put them in the __init__.py file.

Answer 2

Your question isn't really about distutils packages, but about Python packages -- a related but different thing with the same name. Packages in Python are a separate kind of module, that are directories with an __init__.py file. You created a person package with a person module with a Person class. import person gives you the package. If you want the person module inside the person package, you need import person.person. And if you want the Person class inside the person module inside the person package, you need from person.person import Person.

These things get a lot more obvious when you don't give different things the same name, and also when you don't put classes in separate modules for their own sake. Also see http://stackoverflow.com/questions/2098088/should-i-create-each-class-in-its-own-py-file