[Tutor] Understanding the error "method got multiple values for keyword argument "
__peter__ at web.de
Wed Mar 1 05:50:10 EST 2017
Alan Gauld via Tutor wrote:
> 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)))
>> 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 )
I think total(name="John", *(1, 2, 3))
is rather resolved as
total(1, 2, 3, name="John")
so that the first argument is both 1 and "John". I conclude that from
>>> def total(name, other):
... print("name:", name, "other:", other)
>>> total(other=42, "John")
File "<stdin>", line 1
SyntaxError: non-keyword arg after keyword arg
>>> total(other=42, *["John"])
('name:', 'John', 'other:', 42)
But this is tricky, and I usually resort to trial-and-error when I run into
> 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
>> 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.
More information about the Tutor