Creating an Instance of a Class with a variable in Python

Question

Hi,

I had this question posted earlier, but it wasn't very clear, and I had trouble with the answers. Since I edited it to make MUCH more sense it seems that people haven't been looking at it, perhaps because they see it already has 6 answers. So I'm re=-posting it here:

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I'm still new to Python and Programming in general, so I need simple explanations! I don't even know what this dictionary thing you're talking about is!

I'm trying to create a game for my little sister. It is a Virtual Pet sort of thing and the Pet has toys to play with.

I created a class Toy and want to create a function, getNewToy(name, data1, data2, data3, data4, data5).

I want this function to create a new instance of the class Toy, and I want the function to be able to be called multiple times each time creating a new instance.

In my experience you create an instance with:

class Toy:
    def __init__(self, name, data1, data2, data3, data4, data5):
        pass

myToy = Toy(myToy, 1, 2, 3, 4, 5)

then to use methods from the class with:

myToy.method1()

Seeing as I want to have the ability to have multiple toys, each with a playWith() method I want the instance to reflect the name of the Toy each time one is called.

I want the instance to be different each time I call the method getNewToy(,...) and the instance to reflect the name.

Remember I'm new to programming, so can you keep explanations simple.

Thank you very much, it's much easier to understand now!

Answer 1

There is no point in making a special getNewToy function. Just create the class:

 newtoy = Toy(name, data1, data2, data3, data4, data5)

That's all you need to do.

"method I want the instance to reflect the name of the Toy each time one is called."

class Toy:
    def __repr__(self):
        return "<type Toy name=%s>" % self.name

Answer 2

I don't see why you need a getNewToy method. Every time you call Toy() you will get a new instance of your class. You probably want code like this:

class Toy: 
    def __init__(self, name, data1, data2, data3, data4, data5): 
        self.name = name
        self.data1 = data1
        # ...

myToy = Toy("firsttoy", 1, 2, 3, 4, 5)
myToy2 = Toy("2ndToy", 6, 7, 8, 9, 10)

Answer 3

Heres how I would do what you explained:

# The following two classes are toys, both have a playWith 
# as you wanted, each playWith do different things
class Ball:
    def __init__(self):
        self.name = "ball"

    def playWith(self):
        print "the ball bounces"

class Car:
    def __init__(self):
        self.name = "car"

    def playWith(self):
        print "the car is fast"

# This is a Python generator, every time .next() is called on it,
# the next "yield-value" is returned
def generator():
    while True:
        yield Ball()
        yield Car()

# This is the creator, it has to be a class rather than a function
# since you wanted a new toy each time getNewToy is called
# and as such the generator needs to be tracked
class ToyCreator:
    def __init__(self):
        self.generator = generator()

    def getNewToy(self):
        return self.generator.next()

# Create five toys, print their name and play with them
# Do note here that even though we ask for five toys but only have
# two "yields" in the generator, the generator "wraps around" (since,
# internally, its just an endless loop) 
toyCreator = ToyCreator()
for i in range(5):
    toy = toyCreator.getNewToy()
    print "Toy",i,toy.name,"\t:",
    toy.playWith()

If youre having trouble understanding the yield business, take a look at the documentation for the python generator.

What youre trying to do is implement a design pattern, a factory pattern, to be more precise.

Still feeling confused? Read again, think a little but dont hesitate to ask. Were here to help. :)

Answer 4

Perhaps you will always have 5 data items, but even if so, consider using *args:

class Toy:
    def __init__(self, name, *args):
        self.name = name
        self.data = args