#! /usr/bin/env python

"""
This file intended to be used within an interactive instruction session

It also happens to be an example of bad programming style yet useful
for a training session.
"""


VERBOSE = True
#VERBOSE = None


class Breakfast2:
    serving = None
    skipping = None
    ordered = None

    def __init__(self):
        self.serving = ["spam & eggs", "toast"]
        self.skipping = []

if VERBOSE: print """
Avoid subtle Python behavior: avoiding data sharing

	Multiple instances of a class may avoid sharing of data by
        assigning values "on demand" within any method, such as the
        constructor.
"""

alice = Breakfast2()
bob = Breakfast2()


if VERBOSE: print """
	Now, they still have identical content...
"""

if bob.serving == alice.serving:
    print "Yes.  Both Bob and Alice have identical VALUES."
else:
    print "No.  Bob and Alice have different values."


if VERBOSE: print """
	Each references a DIFFERENT object!
"""

if bob.serving is alice.serving:
    print "Yes.  Both Bob and Alice REFERENCE the SAME data."
else:
    print "No.  Bob and Alice REFERENCE DIFFERENT data."



if VERBOSE: print """
	Unlike when defined within class definition, these are no
longer identical:
"""

bob.skipping.append("spam")
print "Bob skipping:", bob.skipping
print "Alice skipping:", alice.skipping

if VERBOSE: print """
	As with the example of creating class attributes "on demand"
this time, these were created with initial values of None.  As a result,
assigning one may be done without effecting the other.
"""

bob.ordered = 1
print "Bob ordered:", bob.ordered
print "Alice ordered:", alice.ordered

#End.