How to create a function that takes dictionary inputs?

Question

I am using a module for a project, I have to pass a function to the module and the model does something like:

class module:
   def __init__(self, function, dictionary):
       # dictionary is {'x':2, 'y':4, 'z':23}
       function(**dictionary)

And my function is something like:

def function(*foo):
    return sum(foo)

The problem is that, the module needs named variables, and will pass it to the function like an unpacked dictionary, and the number of elements in dictionary can be variable, so I cannot pre-write the function as def function(x,y,z): return sum(x,y,z), and this raises an error. I do not wish to modify the module, because then, the code will not be universal. How can I solve this problem by just changing my code?

EDIT: I need foo as a list to use in the function

The first argument of `__init__` is always `self`. – Klaus D. Jul 27 '19 at 05:05 — Klaus D., Jul 27 '19 at 05:05

score 3 · Accepted Answer · answered Jul 27 '19 at 05:27

You module that you can't change is calling your function with:

function(**dictionary)

You won't be able to write your function to the argument is a list — it's not being passed a list. You can accept the keywords as a dict and the easily make a list. Your function just needs to be prepared to be called that way:

def f(**foo):

This leads to:

class module:
    def __init__(self, function, dictionary):
       # dictionary is {'x':2, 'y':4, 'z':23}
       function(**dictionary)

def f(**foo):
    print(sum(foo.values()))

module(f, {'x':2, 'y':4, 'z':23})

# prints 29 as expected

score 0 · Answer 2 · edited Jul 27 '19 at 05:23

0

It seems you want the sum of the values:

   def __init__(self, function, dictionary):
       # dictionary is {'x':2, 'y':4, 'z':23}
       function(dictionary.values())

The dictionary.values() will give a list of [2, 4, 23] for your example.

edited Jul 27 '19 at 05:23

shiv_90

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answered Jul 27 '19 at 05:07

Hai Vu

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I don't think you have understood, I **cannot** edit the module – ѕняєє ѕιиgнι Jul 27 '19 at 05:15
So, you cannot change `module`, can you change `function`? – Hai Vu Jul 27 '19 at 05:25
Yes, I can change `function` – ѕняєє ѕιиgнι Jul 27 '19 at 05:27
1

Then see solution from Mark Myer – Hai Vu Jul 27 '19 at 05:31

score 0 · Answer 3 · answered Jul 27 '19 at 05:13

0

def function(*args,**Kwargs):
    try:
        return sum(*args)
    else:
        return sum(**kwargs.values())

double * unpacked dictionary values, and one * is to unpacked anything(except dictionary).

answered Jul 27 '19 at 05:13

Pedro Dalcolli

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score 0 · Answer 4 · answered Jul 27 '19 at 05:22

The number and type of arguments are determined by code of function init In your case this a single argument of type dictionary. So you have always to pass such function f(x) where x is a dictionary. So the that is function f that deals with the argument. E.g.

def fsum(x): return sum(x.values())
...
__init__(fsum, {'a': 1, 'b': 2, 'c': 3})

How to create a function that takes dictionary inputs?

4 Answers4