I'm trying to create a set of states for a Node class. Normally, I would do this by setting each Node instance's state variable to an int, and document which int corresponds to which state (since I don't have enums).
This time, I'd like to try something different, so I decided to go with this:
class Node:
state1 = 1
state2 = 2
def __init__(self):
...
This works well. However, I run into a problem where I have a LOT of states - too many to manually type out. Further, with that many states, I might make an error and assign the same int to two states. This would be a source of bugs when testing for states (e.g.: if self.state==Node.state1 might fail if Node.state1 and Node.state2 were both 3).
For this reason, I would like to do something like this:
class Node:
def __init__(self):
...
...
for i,state in enumerate("state1 state2".split()):
setattr(Node, state, i)
While this would fix human errors in assigning values to states, it's quite ugly, as class variables are being set outside the class definition.
Is there a way I could set class variables within the class definition in this manner? I would ideally like to do this:
class Node:
for i,state in enumerate("state1 state2".split()):
setattr(Node, state, i)
... but that won't work as Node hasn't been defined yet, and will result in a NameError
Alternatively, do enums exist in python3.3?
I'm on Python3.3.2, if it matters
If your only problem with doing the setattr after the class definition is that it's ugly and in the wrong place, what about using a decorator to do it?
def add_constants(names):
def adder(cls):
for i, name in enumerate(names):
setattr(cls, name, i)
return cls
return adder
@add_constants("state1 state2".split())
class Node:
pass