class with changing parameters

I want to define a Python class that accepts different variables as input. However I only want to declare one of them when calling the class, because the variables determine each other and in different situations I have different inputs at hand. So it should be something like a class price that I call as:

foo = price(dollar=10)  
bar = price(euro=20)

and I have a function inside the class that takes the different currencies and translates them into each ot开发者_Python百科her. How do I do that?

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You should use dictionary for keyword arguments. Here is how you can define it in constructor:

class Price:
    def __init__(self, **kwargs):
        if 'dollar' in kwargs and 'euro' in kwargs:
           raise Exception(..)
        if 'dollar' in kwargs:
            self.dollar = kwargs['dollar']
        elif 'euro' in kwargs:
            self.euro = kwargs['euro']
        else:
            raise Exception()