multiple values for keyword argument

[Tobias Blass]

On Sat, 29 Jan 2011, Peter Otten wrote:

>Tobias Blass wrote:
>
>> 
>> 
>> On Sat, 29 Jan 2011, Francesco Bochicchio wrote:
>> 
>>>On 29 Gen, 12:10, Tobias Blass <tobiasbl... at gmx.net> wrote:
>>>> Hi all
>>>> I'm just learning python and use it to write a GUI (with Tkinter) for a
>>>> C program I already wrote. When trying to execute the program below I
>>>> get the following error message.
>>>>
>>>> Traceback (most recent call last):
>>>> File "./abirechner.py", line 64, in <module>
>>>> win =MainWin()
>>>> File "./abirechner.py", line 43, in __init__
>>>> self.create_edit(row=i);
>>>> TypeError: create_edit() got multiple values for keyword argument 'row'
>>>>
>>>> I don't really understand why create_edit gets multiple values, it gets
>>>> one Integer after another (as I see it)
>>>> Thanks for your help
>
>>>> class MainWin(Frame):
>>>>     def create_edit(row,self):
>
>>>Try this:
>>>>         def create_edit(self, row):
>
>> Ok it works now. So the problem was that python requires 'self' to be the
>> first parameter?
>
>When you invoke a method Python implicitly passes the instance as the first 
>positional parameter to it, regardless of the name:
>
>>>> class A:
>...     s = "yadda"
>...     def yadda(but_i_dont_want_to_call_it_self):
>...             print but_i_dont_want_to_call_it_self.s
>...
>>>> A().yadda()
>yadda
>
>You can provoke the same error with a function:
>
>>>> def f(a, b):
>...     pass
>...
>>>> f(1, b=2)
>>>> f(a=1, b=2)
>>>> f(2, a=1)
>Traceback (most recent call last):
>  File "<stdin>", line 1, in <module>
>TypeError: f() got multiple values for keyword argument 'a'
>
>You can think of argument binding as a two-step process.
>At first positionals are bound to the formal parameters in the order of 
>appearance from left to right; then named arguments are bound to parameters 
>with the same name. If a name is already catered by a positional argument 
>(or a name doesn't occur at all and doesn't have a default value) you get an 
>Exception.
>
>
Thanks for your replies, as soon as I knew that python always passes the object
reference as first parameter everything was clear (It's just like argc and argv
in C, you could also call argc fish and argv chips)