How to put a variable into Python docstring

Question

So I'm trying to create a "dynamic" docstring which is something like this:

ANIMAL_TYPES = ["mammals", "reptiles", "other"]

def func(animalType):
""" This is a sample function.

    @param animalType: "It takes one of these animal types %s" % ANIMAL_TYPES
"""

to basically let the docstring for @param animalType show whatever ANIMAL_TYPES has; so that when this variable is updated, the docstring will be updated automatically.

Unfortunately, it doesn't seem to work. Does anyone know if there is a way of achieving this?

Answer 1

One way to do this would be to use a decorator. I'm not sure how I feel about this; I actually searched for commentary on this method and found this answer, which rightly notes that it could mask a design problem. But your use case seems sound to me at first glance.

In any case, here's a fairly elegant way to achieve the result you're looking for:

>>> def docstring_parameter(*sub):
...     def dec(obj):
...         obj.__doc__ = obj.__doc__.format(*sub)
...         return obj
...     return dec
... 
>>> @docstring_parameter('Ocean')
... def foo():
...     '''My Docstring Lies Over The {0}'''
...     pass
... 
>>> @docstring_parameter('Sea')
... def bar():
...     '''My Docstring Lies Over The {0}'''
...     pass
... 
>>> @docstring_parameter('Docstring', 'Me')
... def baz():
...     '''Oh Bring Back My {0} To {1}'''
...     pass
... 
>>> foo.__doc__
'My Docstring Lies Over The Ocean'
>>> bar.__doc__
'My Docstring Lies Over The Sea'
>>> foo.__doc__
'My Docstring Lies Over The Ocean'
>>> baz.__doc__
'Oh Bring Back My Docstring To Me'