CODEWITHSUNDEEP
pythonreturnglobal
dmvianna
dmvianna

Reputation: 15718

nested function returning outer function

I have a common pattern that goes like

def f(x):
  if x.type == 'Failure':
     # return `x` immediately without doing work
     return x
  else:
  # do stuff with x...
  return x

I would like to abstract the if/else pattern into a stand alone function. However I want that function, when called from inside f, to return from f immediately. Else it should just return x to a value inside f for further processing. Something like

def g(x):
  if x.type == 'Failure':
    global return x
  else:
    return x.value

def f(x):
  x_prime = g(x) # will return from f
                 # if x.type == 'Failure'
  # do some processing...
  return x_prime

Is this possible in Python?

Upvotes: 1

Views: 1888

Answers (1)

dmvianna
dmvianna

Reputation: 15718

I'm using Validation from my branch of pycategories:

def fromSuccess(fn):
    """
    Decorator function. If the decorated function
    receives Success as input, it uses its value.
    However if it receives Failure, it returns
    the Failure without any processing.
    Arguments:
        fn :: Function
    Returns:
        Function
    """
    def wrapped(*args, **kwargs):
        d = kwargs.pop('d')
        if d.type == 'Failure':
            return d
        else:
            kwargs['d'] = d.value
        return fn(*args, **kwargs)
    return wrapped

@fromSuccess
def return_if_failure(d):
    return d * 10

return_if_failure(d = Failure(2)), return_if_failure(d = Success(2))

>>> (Failure(2), 20)

Upvotes: 2

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