Dictionary with classes?

Question

In Python is it possible to instantiate a class through a dictionary?

shapes = {'1':Square(), '2':Circle(), '3':Triangle()}
x = shapes[raw_input()]

I want to let the user pick from a menu and not code huge if else statements on the input. For example if the user entered 2, x would then be a new instance of Circle. Is this possible?

• S.Lott: When you tried it, what happened?
• mandroid: Well I'm doing it with menu's, and just having a generic menu wrapper handle what menu to load up. I'm very new to this :-/
• Markus: Yes, it's possible, and you're doing it right PROVIDED you want to instantiate all the shapes once at the beginning, store the instances in the dict and have one of them assigned to x. If you want to only instantiate the selected class, or you plan on instantiating individual shapes multiple times, use something like Vinay's answer.

Answer 1

Almost. What you want is

shapes = {'1':Square, '2':Circle, '3':Triangle} # just the class names in the dict
x = shapes[raw_input()]() # get class from dict, then call it to create a shape instance.

Answer 2

I'd recommend a chooser function:

def choose(optiondict, prompt='Choose one:'):
 print prompt
 while 1:
 for key, value in sorted(optiondict.items()):
 print '%s) %s' % (key, value)
 result = raw_input() # maybe with .lower()
 if result in optiondict:
 return optiondict[result]
 print 'Not an option'
result = choose({'1': Square, '2': Circle, '3': Triangle})()