[Tutor] Understanding the error "method got multiple values for keyword argument "

[Alan Gauld]

On 01/03/17 08:18, Pabitra Pati wrote:

>     def total(name, *args):
>         if args:
>             print("%s has total money of Rs %d/- " %(name, sum(args)))
>         else:
>             print("%s's piggy bank  has no money" %name)
> 
> I can call this method passing the extra arguments inside *().
> *I know the correct way of passing the arguments.* But, I am passing value
> for 'name' in form of param=value, *intentionally*, 

So you expected to get an error?
So what exactly are you asking about? Which error did
you think you would get?

Remember that you are not allowed to pass positional
arguments after you pass a named argument. So python
sees your call as something like:

total(name = "John", 1, 2, 10 )

ie as 4 arguments being passed to name and
*args and can't figure out where name stops and
*args begins. It could be any of:

total( name=("John", 1),  2, 10 ) or
total( name=("John", 1, 2),  10 ) or
total( name=("John", 1, 2, 10)  )  # empty *args is allowed.

The whole point of *args is that they represent unnamed
arguments, you may not put named arguments in front of
them, it's illegal.

> However, I am unable to understand the below error message :-
> 
>     >>> total(name="John", *(1, 2, 10) )
>     Traceback (most recent call last):
>       File "<stdin>", line 1, in <module>
>     TypeError: total() got multiple values for keyword argument 'name'
> 
> How Python is evaluating the above call, that it's getting multiple values
> for the parameter 'name'?  How the call is being interpreted internally?

If you want the technical details of how the interpreter
is working there are others better qualified to explain,
but since what you are trying to do is not valid Python
I'm not sure there is much point in analyzing it.

-- 
Alan G
Author of the Learn to Program web site
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