Exposing optional arguments of a nested method in python

Question

A similar question has been asked before but I don't know that I like the answer. You have a parent function, which calls a child function.

def parent(a):
   return child(a) * 2

def child(a, b=10, c=20):
   return a + b + c

If I want the parent method to expose b and c, I can do something like below. It works, but seems cumbersome, as I'm reaching for it a lot (maybe that suggests some other problem).

def parent(a, b=None, c=None):

    kwargs = {}
    if b is not None:
        kwargs['b']=b
    if c is not None:
        kwargs['c']=c

    return child(a, **kwargs)

Is there a better (i.e. less code) way to do this?

Where was it asked before? Place a bounty on that question asking for new answers. — jonrsharpe
– jonrsharpe, Commented Jan 16, 2019 at 20:05
Why don't you set the default values for b and c in parent() to the default values of b and c in child()? Then you can just call child(a=a, b=b, c=c). — 9769953
– 9769953, Commented Jan 16, 2019 at 20:08
I may be mistaken but right now isn't parent identical to child? parent = child has the exact same functionality? — Primusa
– Primusa, Commented Jan 16, 2019 at 20:08
@9769953 child was defined earlier. the defaults for child make sense. what if other methods want to call child? I want them to also have access to those sensible defaults — compguy24
– compguy24, Commented Jan 16, 2019 at 20:10
seems that this isn't a duplicate after all. OP is aware of the solutions, and it looks not that good. Besides the question is more generic and understandable — Jean-François Fabre
– Jean-François Fabre ♦, Commented Jan 16, 2019 at 20:11

Brad Fallon · Accepted Answer · 2019-01-16 20:16:49Z

3

If parent and child are both your own functions, then you could have the default values defined as a constant that is shared for both functions.

B_DEF = 10
C_DEF = 20

def parent(a, b=B_DEF, c=C_DEF):
   return child(a,b,c) * 2

def child(a, b=B_DEF, c=C_DEF):
   return a + b + c

edited Jan 16, 2019 at 20:16

answered Jan 16, 2019 at 20:12

Brad Fallon

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