What's a good way to provide additional decoration/metadata for Python function parameters?

Question

We\'re considering using Python (IronPython, but I don\'t think that\'s relevant) to provide a sort of \'macro\' support for another application, which controls a piece of equip

Answer 1

I would use some kind of decorator:

class TypeProtector(object):
    def __init__(self, fun, types):
        self.fun, self.types = fun, types
    def __call__(self, *args, **kwargs)
        # validate args with self.types
        pass
        # run function
        return fun(*args, **kwargs)

def types(*args):
    def decorator(fun):
        # validate args count with fun parameters count
        pass
        # return covered function
        return TypeProtector(fun, args)
    return decorator

@types(Time, Temperature)
def myfunction(foo, bar):
    pass

myfunction('21:21', '32C')
print myfunction.types

Answer 2

Decorators are a good way to add metadata to functions. Add one that takes a list of types to append to a .params property or something:

def takes(*args):
    def _takes(fcn):
        fcn.params = args
        return fcn
    return _takes

@takes("time", "temp", "time")
def do_stuff(start_time, average_temp, stop_time):
    pass

Answer 3

For python 2.x, I like to use the docstring

def my_func(txt):
    """{
    "name": "Justin",
    "age"   :15
    }"""
    pass

and it can be automatically assign to the function object with this snippet

for f in globals():
    if not hasattr(globals()[f], '__call__'):
        continue
    try:
        meta = json.loads(globals()[f].__doc__)
    except:
        continue
    for k, v in meta.items():
        setattr(globals()[f], k, v)

Answer 4

The 'pythonic' way to do this are function annotations.

def DoSomething(critical_temp: "temperature", time: "time")
    pass