18.2

class PiClass:
    def __str__(self):
        return "PI"
pi = PiClass()

18.3
>>> mathproj.comp.numeric.n1
Traceback (most recent call last):

18.3.1 Basic use of mathproj

>>> import mathproj
Hello from mathproj init

>>> mathproj.version
1.03

18.3.2 Loading subpackages

>>> import mathproj
>>> mathproj.comp.numeric.n1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'comp'

>>> import mathproj.comp.numeric.n1
Hello from mathproj.comp init
Hello from numeric init
>>> mathproj.comp.numeric.n1.g()
version is 1.03
Called function h in module n2

>>> mathproj.comp
<module 'mathproj.comp' from 'mathproj/comp/__init__.py'>
>>> mathproj.comp.numeric
<module 'mathproj.comp.numeric' from 'mathproj/comp/numeric/__init__.py'>

18.3.3 import statements within packages

from mathproj import version
from mathproj.comp import c1
from mathproj.comp.numeric.n2 import h
def g():
    print "version is", version
    print h()

from ... import version
from .. c1 import x
form . n2 import h

18.4 The __all__ attribute

>>> from mathproj import *
Hello from mathproj init
Hello from mathproj.comp init
>>> comp
<module 'mathproj.comp' from 'mathproj/comp/__init__.py'>

>>> c1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'c1' is not defined

>>> from mathproj.comp import c1
>>> c1
<module 'mathproj.comp.c1' from 'mathproj/comp/c1.py'>