[EMAIL PROTECTED] wrote:
> Hello. Please tell me whether this feature request is sane (and not
> done before) for python so it can be posted to the python-dev mailing
> list. I should say first that I am not a professional programmer with
> too much technical knowledge.
>
> I would like to have something like the "option explicit" statement in
> Visual Basic which turns on C-like checking for declaration of
> variables. This is highly helpful for people who are coming from C/C+
> +, for people who are learning programming using Python, and even
> professionals, since this helps prevent typo errors like:
>
> sunlognitude = sunlongitude + 180.0
>
> where the user has inadvertantly typed "g" before "n" and will later
> wonder why his application is not working as expected.
>
I have no formal training in programming and thus have had to shake off
all of the worst habits afflicting amateurs on my path to the modest
proficiency I enjoy now. So let me assure you that this is something I
can honestly say is just about the least of your worries and
consequently has no place clogging up a language like python.
But, if you have masochistic tendencies and want a lot of overhead in
your programming, you can always bind yourself mercilessly to classes:
class C(object):
declared = ['bob', 'carol', 'ted', 'alice']
def __setattr__(self, anattr, aval):
if anattr not in C.declared:
raise TypeError, "Just can't hook you up, bro."
else:
self.__dict__[anattr] = aval
E.g.:
py> class C(object):
... declared = ['bob', 'carol', 'ted', 'alice']
... def __setattr__(self, anattr, aval):
... if anattr not in C.declared:
... raise TypeError, "Just can't hook you up, bro."
... else:
... self.__dict__[anattr] = aval
...
py> c = C()
py> c.bob = 42
py> c.bob
42
py> c.x = 69
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 5, in __setattr__
TypeError: Just can't hook you up, bro.
Extending this ugliness to type-checking is left as an exercise for the
reader. Using metaclasses for such nonsense is left as an exercise for
metaclass maniacs.
James
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