"no variable or argument declarations are necessary."

[Antoon Pardon]

Op 2005-10-05, Duncan Booth schreef <duncan.booth at invalid.invalid>:
> Paul Rubin wrote:
>
>> Brian Quinlan <brian at sweetapp.com> writes:
>>> Have those of you who think that the lack of required declarations in
>>> Python is a huge weakness given any thought to the impact that adding
>>> them would have on the rest of the language? I can't imagine how any
>>> language with required declarations could even remotely resemble
>>> Python.
>> 
>> What's the big deal?  Perl has an option for flagging undeclared
>> variables with warnings ("perl -w") or errors ("use strict") and Perl
>> docs I've seen advise using at least "perl -w" routinely.  Those
>> didn't have much impact.  Python already has a "global" declaration;
>> how does it de-Pythonize the language if there's also a "local"
>> declaration and an option to flag any variable that's not declared as
>> one or the other?
>
> The difference is that perl actually needs 'use strict' to be useful for 
> anything more than trivial scripts. Without 'use strict' you can reference 
> any variable name without getting an error. Python takes a stricter 
> approach to begin with by throwing an exception if you reference an 
> undefined variable.
>
> This only leaves the 'assigning to a different name than the one we 
> intended' problem which seems to worry some people here, and as has been 
> explained in great detail it incurs a cost to anyone reading the code for 
> what most Python users consider to be a very small benefit.

It also is one possibility to implement writable closures.

One could for instace have a 'declare' have the effect that
if on a more inner scope such a declared variable is (re)bound it
will rebind the declared variable instead of binding a local name.

-- 
Antoon Pardon