Idea about method parameters

Markus Schaber markus at schabi.de
Wed Sep 26 21:40:40 CEST 2001


Hi,

Wolfgang Grafen <wolfgang.grafen at marconi.com> schrub:

> Well, Python is flexible to do it anyway and although I missed
> to give an example for that I hoped you could develop by yourself:
> 
>>>> class A:
> ...     def __init__(self,a,b,c=333,d=444):
> ...         self.__dict__.update(vars())
> ...         del self.__dict__['self'] # remove cyclic self reference
> ...     def __call__(self):
> ...         print self.a, self.b, self.c, self.d

I had such in mind, yes. Your solution is more elegant (especially with 
treating the "self"), have my respects.

But it only works if you want to assign _all_ parameters to the 
corresponding instance variables. Every other variable (including self) 
has to be explicitly treated. In a mixed-case, the "good old" way is 
less work and less "obfuscated".

My example in Message <1634093.6GMIcojqen at lunix.schabi.de> shows such a 
mixed case (although most of the variables are assigned).

[snip]

> Answers to your objections (below):
> 1. Now the parameter list is under the programmer's control
> 2. Using self.__dict__ is *not* a dirty hack as already many code
>    does use self.__dict__
> 3. Positional parameters are possible as well
> 4. There are default values
> 5. No need for an extra documentation of valid parameters

Fully agree on 1, 3, 4 and 5. 

I still consider accessing self.__dict__ somehow hackish - but maybe 
that is because of my "static" history. And as it seems that it is 
common sense, have my +0.99 :-)
 
> For me this is good enough and there is no need for a new syntax.

The old way with explicit assignments is also "good enough", as it 
works and is well-known.

But for loops are also "good enough" to replace mapping and list 
comprehensions, but they still found their way in the language.

One may also create a dictionary using lots of d[key]=value statements, 
so there's no need to recycle those curly braces known from C :-)

Don't get me wrong, I love those constructs (Dictionaries, mapping, 
list comprehensions and even self.__dict__) - they constitute the 
pythonic way of life :-)

But having a "good enough" way should not be a killer argument for a 
better possibility. Although your solution is a good argument against 
my proposal.

markus
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"The strength of the Constitution lies entirely in the determination of 
each citizen to defend it. Only if every single citizen feels duty 
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