OO Bug needs squashing

[David Goodger]

nick wrote:
 > Ok I'm more than willing to admit it's probably me but I am
 > struggling with what appears to be a weird scope issue.
 >
 > If you look at the code below I believe day 2 should only contain a
 > single event. But when you run the prog it prints the events from
 > day 1 as well.
 >
 > Any advice greatly appreciated.

First, don't use hard tabs.  The standard is to use 4 spaces per
indent level.

 > class Day:
 >     name = None
 >     events = []
 >     eventD = {}

These are class attributes.  They're shared by all instances of
that class.  "events" and "eventD" are mutable, which means that
they can change.

Instead, move events and eventD into an initializer method:

       def __init__(self):
           self.events = []
           self.eventD = {}

You should also use the __init__ method to populate the object:

       def __init__(self, name):
           self.events = []
           self.eventD = {}
           self.name = name

 > class Event:
 >     start = ''
 >     end = ''
 >     desc = ''

       def __init__(self, start, end, desc):
           self.start = start
           self.end = end
           self.desc = desc

 > def loadMonth():
 >     #Create Day one
 >     day1 = Day()
 >     day1.name = 'day1'

Instead of the last 2 lines, use:

       day1 = Day('day1')

 >     #Create first event for day one
 >     event1 = Event()
 >     event1.start = '10:00'
 >     event1.end = '12:00'
 >     event1.desc = 'event1'

Instead of the last 4 lines, use:

       event1 = Event('10:00', '12:00', 'event1')

 >     day1.events.append(event1)

That should be a method instead:

       day1.add_event(event1)

The method would look like this (add under "class Day"):

       def add_event(self, event):
           self.events.append(event)

That way, if you choose to change the implementation of
the events storage later, it will be easy.

And so on.  I suggest you look at these pages:

* Python Tutorial: http://www.python.org/doc/current/tut/
* the FAQ: http://www.python.org/doc/faq/ (especially question 4.21 of
   http://www.python.org/doc/faq/general.html, which directly answers
   your original question)
* lots more links here: http://www.python.org/topics/learn/

-- David Goodger