There is an interesting skewness in python:
class A(object): pass
>>a=A()
setattr(a, '$foo', 17)
getattr(a, '$foo')
17
But I can't write
>>a.'$foo'
5  1359  sz****@gmail.co m wrote:
There is an interesting skewness in python:
class A(object): pass
>>>a=A()
setattr(a, '$foo', 17)
getattr(a, '$foo')
17
But I can't write
>>>a.'$foo'
Yes, this is known. I think IronPython uses a specialized dictionary for members, which prohibits
malformed names. I don't know if there will be such a dictionary in any future CPython version.
(Would be good.)
panzi sz****@gmail.co m wrote:
There is an interesting skewness in python:
class A(object): pass
>a=A()
setattr(a, '$foo', 17)
getattr(a, '$foo')
17
But I can't write
>a.'$foo'
Likewise, you can write
setattr(a,'hell o',17)
but you can't write
a.'hello'
but you can write
a.hello
The only thing that can follow the "." (attribute access) operator is a
valid Python identifier. Strings may not. Anyways, it's probably not
a good idea in most cases to use getattr and setattr with a
non-identifier, but Python doesn't prevent you from doing it. (Which
is good in the occasional case where it is a good idea.)
BTW, Matlab has an interesting syntax; you could have written this:
a.("$foo")
(And because Matlab is weird that way, this was not structure member
access, but some weird hybrid of structure accces and indexing and/or
slicing. The syntax was very useful in Matlab because there's no
built-in associative array and using this syntax was the easiest way to
get something like it. In Python we'd do that with a dict, so it's not
so useful here.)
Carl Banks
Le 21 Nov 2006 13:21:52 -0800, sz****@gmail.co m a écrit :
There is an interesting skewness in python:
class A(object): pass
>a=A()
setattr(a, '$foo', 17)
getattr(a, '$foo')
17
But I can't write
>a.'$foo'
Well, you can even do :
>>class A(object): pass
....
>>a = A()
setattr(a, 'some.attr', 15)
a.some.attr
Traceback (most recent call last):
File "<stdin>", line 1, in ?
AttributeError: 'A' object has no attribute 'some'
>>getattr(a, 'some.attr')
15
>>>
Which is a lot funnier IMHO :)
- Jon
On Tue, 21 Nov 2006 22:39:09 +0100, Mathias Panzenboeck wrote: sz****@gmail.co m wrote:
>There is an interesting skewness in python:
class A(object): pass
>>>>a=A()
setattr(a , '$foo', 17)
getattr(a , '$foo')
17
But I can't write
>>>>a.'$foo'
Yes, this is known. I think IronPython uses a specialized dictionary for members, which prohibits
malformed names. I don't know if there will be such a dictionary in any future CPython version.
(Would be good.)
Why would it be good?
How many bugs have you found that were caused by this behaviour?
--
Steven D'Aprano
Steven D'Aprano wrote:
On Tue, 21 Nov 2006 22:39:09 +0100, Mathias Panzenboeck wrote:
Yes, this is known. I think IronPython uses a specialized dictionary for members, which prohibits
malformed names. I don't know if there will be such a dictionary in any future CPython version.
(Would be good.)
Why would it be good?
How many bugs have you found that were caused by this behaviour?
It's not bugs. A specialized dictionary could be better optimized if
you know it can only hold Python identifiers. There's talk of such a
dictionary in Python 3000.
Carl Banks This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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