How to use a string as a function parameter in Python and have variable number of parameters

Question

I have a function called filter that accepts a number of parameters in the format name=value. I have 2 lists: names and values (let's call them x and y), I need to be able to pass these into the function.

When I just pass in the string as in the below example, it gives me an error:

x = ['t', 't2']
y = [w, w2]
filter(x[0]=y[0], x[1]=y[1])

SyntaxError: keyword can't be an expression

I would also need to be able to pass in an arbitrary amount, for the size of the lists. How can I go about making this work?

Post the function declaration, please... It's hard to tell what you are expecting — Pedro Martins de Souza, Dec 21 '18 at 16:44
Not sure how you have defined your filter but it seems you can just pass arguments as `filter(y[0],y[1])` — mad_, Dec 21 '18 at 16:46

score 3 · Accepted Answer · answered Dec 21 '18 at 16:46

3

Use **kwargs:

kwargs = {x[0]: y[0], x[1]: y[1]}
filter(**kwargs)

answered Dec 21 '18 at 16:46

iBug

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Thanks so much, this was exactly it lol. New to kwargs, I thought I could pass in a dictionary but it wasn't really working before. – Supez38 Dec 21 '18 at 16:53

score 0 · Answer 2 · answered Dec 21 '18 at 16:46

0

You probably don't want to have a function called filter as that will overwrite the built-in python filter function. But otherwise read up on using *args and **kwargs, sounds like what you need.

answered Dec 21 '18 at 16:46

bjk116

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Yeah, that was it. Thanks – Supez38 Dec 21 '18 at 16:57

How to use a string as a function parameter in Python and have variable number of parameters

2 Answers2