Newbie class instance tracking system

[Lyle Johnson]

> I am new to Python and I am having trouble with the following code.  In
short,
> Why doesn't it work?  I thought that variable names "spring into
existence" in
> a similar fasion to perl...

Although Python's error message wasn't very helpful in this case, the
problem was that for a new key (or car company name) in the dictionary, you
didn't specify the data type (which in your case should be a list). I've
modified your code (shown below) to initialize the dictionary entry to an
empty list if it encounters a new key; the relevant lines are:

        if not Maker.all_cars.has_key(carCompany):
            Maker.all_cars[carCompany] = []

Hope this helps,

Lyle

class Maker:
    all_cars={}

    def __init__(self,carName=None,carCompany=None):
        self.carName = carName
        self.carCompany = carCompany
        if not Maker.all_cars.has_key(carCompany):
            Maker.all_cars[carCompany] = []
        Maker.all_cars[carCompany].append(carName)

prelude = Maker(carName='prelude',carCompany='Honda')
accord = Maker(carName='accord',carCompany='Honda')

for carCompany in Maker.all_cars.keys():
    print "Cars from %s:" % carCompany
    for carName in Maker.all_cars[carCompany]:
        print "    %s" % carName