Fredrik Lundh a écrit :
> [EMAIL PROTECTED] wrote:
>
>
>>For example:
>>
>>
>>>>>A = [] # let's declare a "constant" here
>>>>>b = A # and let's assign the constant here
>>>>>b.append('1') # OOPS!
>>>>>c = A
>>>>>print A
>>
>>['1']
>>
>>>>>print b
>>
>>['1']
>>
>>>>>print c
>>
>>['1']
>>
>>As you can see, the "constant" A can be modified this easily. But if
>>there were an intuitive mechanism to declare a symbol to be immutable,
>>then there won't be this problem.
>
>
> why are you using mutable objects as constants?
>
> (insert obligatory "it hurts when I do this" joke here)
>
> btw, given a hypothetical "object that symbol points to is immutable" syntax,
> what would you expect this to do ?
>
> >>> constant A = []
>
> >>> b = [A]
>
> >>> # much later
> >>> b[0].append('1')
That's easy, since A is a symbolic constant know at compile time, and
since it's a known mutable objet, the code once compiled will be
equivalent to:
>>> b = [[]]
>>> # much later
>>> b|0].append('1')
--
http://mail.python.org/mailman/listinfo/python-list
