Question

I am currently studying programming and I have the following problem.

A user should enter the operation that he wants to do from the command line and according to the operation, he should enter the information about the item.

I have tried things like the following:

def stock(f):
    d={}
    f()
    return d


def add(item,amount):
    d[item]=amount
    return d

Or

def stock(item,amount,f):
    d={}
    if f():
        d[item]=amount
    return d


def add():
    return True

and, second one doesn’t work for me because, when i want to use this code remove(a,b) i don’t need three argument. What i’m trying to say is number of argument changes according to my operations. How do i handle this.

Answer 1

If I understand you correctly, you need a dictionary factory pattern

>>> class Calc(object):
    def __init__(self):
            #Initialize a dictionary of keywords and callbacks
        self.operation = {
            'add':self.add,
            'sub':self.sub,
            'mul':self.mul,
            'div':self.div,
            'neg':self.neg

            }
    #Overload the function call
    def __call__(self, *args):
        return self.operation[args[0]](*args[1:])
    # *args - variable list argument list
    def add(self,*args):
        return sum(args)
    def sub(self,*args):
        return args[1] - args[0]
    def mul(self, *args):
        if len(args) == 0:
            return 1
        elif len(args) == 1:
            return args[0]
        else:
            return args[0] * args[1]
    def div(self, *args):
        return args[0] / args[1]
    def neg(self, *args):
        return -args[0]


>>> calc = Calc()
>>> calc('add',1,2,3)
6
>>> calc('mul',10)
10
>>> calc('mul',10,4)
40
>>> calc('neg',3)
-3
>>>