Passing a list of parameters into a Python function [duplicate]

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What does ** (double star/asterisk) and * (star/asterisk) do for parameters? (28 answers)

Closed 10 years ago.

How would I pass an unknown number of parameters into a function? I have a function defined in the following way

def func(x, *p):
 # do something with variable number of parameters (*p)
 pass

I'm trying to pass in a list of values to use as parameters. I tried using a list and a tuple but the function always returns zero. Has anyone got any advice?

Answer 1

some_list = ["some", "values", "in", "a", "list", ]
func(*some_list)

This is equivalent to:

func("some", "values", "in", "a", "list")

The fixed x param might warrant a thought:

func(5, *some_list)

... is equivalent to:

func(5, "some", "values", "in", "a", "list")

If you don't specify value for x (5 in the example above), then first value of some_list will get passed to func as x param.

• Hedwin Bonnavaud: Hy, do you have an idea of how to do something like: func(first="some", name="values", third="in", another="a", last="list") from a list some_list = [(attr_1, value1), (attr2, value2), ...] or a dict ?

Answer 2

Pass the values as comma separated values

>>> def func(x, *p): # p is stored as tuple
... print "x =",x
... for i in p:
... print i
... return p
... 
>>> print func(1,2,3,4) # x value 1, p takes the rest
x = 1
2
3
4
(2,3,4) # returns p as a tuple

You can learn more by reading the docs