Suppose that I have class C.
I can write o = C() to create an instance of C and assign it to o.
However, what if I want to assign the class itself into a variable and then instantiate it?
For example, suppose that I have two classes, such as C1 and C2, and I want to do something like:
if (something):
classToUse = C1
else:
classToUse = C2
o = classToUse.instantiate()
What's the syntax for the actual instantiate()? Is a call to __new__() enough?
o = C2()
This will accomplish what you want. Or, in case you meant to use classToUse, simply use:
o = classToUse()
Hope this helps.
__call__(). (I hope formatting works this time.)__call__() metamethod. Thanks, Bastien Léonard.apply() had to be used for this purpose before 2.3.You're almost there. Instead of calling an instantiate() method, just call the variable directly. It's assigned to the class, and classes are callable:
if (something):
classToUse = C1
else:
classToUse = C2
o = classToUse()
It's simple, Python don't recognize where a varible is a class or function. It's just call that value.
class A:
pass
B=A
b=B()
A class is an object just like anything else, like an instance, a function, a string... a class is an instance too. So you can store it in a variable (or anywhere else that you can store stuff), and call it with () no matter where it comes from.
def f(): print "foo"
class C: pass
x = f
x() # prints foo
x = C
instance = x() # instanciates C
