arbitrary number of arguments in a python function

Question

I'd like to learn how to pass an arbitrary number of args in a python function, so I wrote a simple sum function in a recursive way as follows: ``` def mySum(*args): if len(args) == 1: return args[0] else: return args[-1] + mySum(args[:-1]) ``` but when I tested `mySum(3, 4)`, I got this error: ``` TypeError: unsupported operand type(s) for +: 'int' and 'tuple' ``` Does anyone have an idea about this and gimme some clue to correct it?

Accepted Answer

This line:

```
return args[-1] + mySum(args[:-1])
```

`args[:-1]` returns a slice of the arguments tuple. I assume your goal is to recursively call your function using that slice of the arguments. Unfortunately, your current code simply calls your function using a single object - the slice itself.

What you want to do instead is to call with those args unrolled.

```
return args[-1] + mySum(*args[:-1])
                        ^---- note the asterisk
```

This technique is called "unpacking argument lists," and the asterisk is sometimes (informally) called the "splat" operator.

arbitrary number of arguments in a python function

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