Limit argument to specific values in python

Question

If I have python function with a string argument which needs to be in a specific list of values, what's the best way to handle this? Is there a convention to expressing this in the docstrings or anything?

eg.

def makeShape(shape):
   assert shape in ["circle", "square", "triangle"]

Is there a nicer way to express that shape should always be one of those three values?

Answer 1

If this is a genuine error, you should raise an exception. I think TypeError would be a reasonable choice, but you may want to define your own.

assert statements are for development. Note that they are ignored when the -O argument is used, so they should not be relied upon to catch errors.