为什么不能在Python中使用变量作为参数来调用此函数？

Question

Example:

def somerando(a,b,c,d):
    if not a+b+c+d == 9000:
        return (a+b+c+d)

somerando(1,2,3,4)

Returns: 10

but

randonumbs = [1,2,3,4]

somerando(randonumbs)

Gives the following error:

TypeError Traceback (most recent call last) in ----> 1 somerando(randonumbs)

TypeError: somerando() missing 3 required positional arguments: 'b', 'c', and 'd'

Answer 1

your function expects 4 arguments. randonumbs = [1,2,3,4] is a list (of four items); that is one argument for your function.

you could do this:

randonumbs = [1,2,3,4]
somerando(*randonumbs)

this usage of the asterisk ( * ) is discussed in this question or in PEP 3132 .

Answer 2

You passed randonumbs as list, means this whole list is considered as first argument to the function somerando
You can use somerando(*randonumbs) .

Here, * means pass as tuple & ** means pass as dictionary (key, value pair) if you use ** in function parameters/ arguments.

Thank you.

Answer 3

The single-asterisk form of *args can be used as a parameter to send a non-keyworded variable-length argument list to functions, like below

randonumbs = [1,2,3,4]
somerando(*randonumbs)

The double asterisk form of **kwargs is used to pass a keyworded, variable-length argument dictionary to a function.

randonumbs = {'a':1, 'b':2, 'c': 3, 'd': 4}
somerando(**randonumbs)