您可以使用Python为您创建一个可以创建一个类的多个实例的函数吗？

Question

I'm trying to figure out some OOP stuff with python and I'm running into a few problems. I'm trying to make a "game" that involves the player walking around a grid of rooms, with each room an instance of the Room class. If I wanted to make a big grid, instantiating each room would be a pain as I could potentially have to type in the same repetitive coordinate pattern for 64 different rooms, so I wanted to make a function that would do it for me, I'm running into problems figuring out how. Here's the code I have:

class Room(object):

    def __init__(self, x, y):
        self.x = x
        self.y = y

def generate_rooms():

    names = [a,b,c,d]
    locations = [[1,1],[1,2],[2,1],[2,2]] #this line could be a few for loops

    for x in range(0,4):
        names[x] = Room(locations[x][0],locations[x][1])

The idea was that this would create 4 Rooms named a, b, c, and d with the coordinates specified in locations. Python won't let me do this because a, b, c, and d aren't defined. In any implementation I've tried I've run into the problem that naming instances needs to be done with variable names, and I wouldn't know how to generate those dynamically.

I've searched around a lot and it doesn't really seem like automation of instantiation is really something people would want to do, which confuses me because it seems like it would really make sense in situations like this.

Any help on how to fix this or on how to accomplish this task in a better way is greatly appreciated!

Answer 1

You're very close! The usual approach is to use a dictionary, and to use the names you want as dictionary keys. For example:

>>> class Room(object):
...     def __init__(self, x, y):
...         self.x = x
...         self.y = y
...         
>>> rooms = {}
>>> names = ['a', 'b', 'c', 'd']
>>> locations = [[1,1], [1,2], [2,1], [2,2]]
>>> for name, loc in zip(names, locations):
...     rooms[name] = Room(*loc)
...     
>>> rooms
{'a': <__main__.Room object at 0x8a0030c>, 'c': <__main__.Room object at 0x89b01cc>, 'b': <__main__.Room object at 0x89b074c>, 'd': <__main__.Room object at 0x89b02ec>}
>>> rooms['c']
<__main__.Room object at 0x89b01cc>
>>> rooms['c'].x
2
>>> rooms['c'].y
1

This way you can iterate over the rooms in several ways, for example:

>>> for roomname, room in rooms.items():
...     print roomname, room.x, room.y
...     
a 1 1
c 2 1
b 1 2
d 2 2

Answer 2

A few thoughts:

Perhaps It would make sense to have a name-field in the Room-class?

What's wrong with a = Room(1,1)? You can store a in an array later. ie declaring the array AFTER you have instantiated the Rooms.

Why do you care about naming at all? Python doesn't care.

Automatic instatiation is trivial and usually done with loops and arrays. Writing programs that modify/create programs is referred to as metaprogramming and is not trivial.

Good luck!

Answer 3

Just minor changes below:

class Room(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y

def generate_rooms():
    names = [a,b,c,d]        // <-- this line goes crazy, since a,b,c,d is not defined yet
    locations = [[1,1],[1,2],[2,1],[2,2]] 

    for x in range(0,4):     // <-- this part can be improved
        names[x] = Room(locations[x][0],locations[x][1])

    // no return here? then what to generate?

def new_generate_rooms():
    locations = [[1,1],[1,2],[2,1],[2,2]]
    rooms = [Room(loc[0], loc[1]) for loc in locations]
    return rooms

def main():
    rooms = new_generate_rooms()
    for i,room in enumerate(rooms):
        print str(i)+'-th room: ', room.x, room.y

I am feeling that you may need to learn more of the pythonic syntax and idioms. Bless.