Nick Craig-Wood wrote:
> Martin Geisler <[EMAIL PROTECTED]> wrote:
>
>> I just tried running my code using "python2.6 -3" and got a bunch of
>>
>> SyntaxWarning: tuple parameter unpacking has been removed in 3.x
>>
>> warnings. I've read PEP-3113:
>>
>> http://www.python.org/dev/peps/pep-3113/
>>
>> but I'm still baffled as to why you guys could remove such a wonderful
>> feature?!
>
> I don't think many people will miss tuple unpacking in def statements.
>
> I think the warning is probably wrong anyway - you just need to remove
> a few parens...
>
>> ci.addCallback(lambda (ai, bi): ai * bi)
>> map(lambda (i, s): (field(i + 1), s), enumerate(si))
>
> On
> Python 3.0rc1 (r30rc1:66499, Oct 4 2008, 11:04:33)
>
>>>> f = lambda (ai, bi): ai * bi
> File "<stdin>", line 1
> f = lambda (ai, bi): ai * bi
> ^
> SyntaxError: invalid syntax
>
> But
>
>>>> f = lambda ai, bi: ai * bi
>>>> f(2,3)
> 6
>
> Likewise
>
>>>> lambda (i, s): (field(i + 1), s)
> File "<stdin>", line 1
> lambda (i, s): (field(i + 1), s)
> ^
> SyntaxError: invalid syntax
>>>> lambda i, s: (field(i + 1), s)
> <function <lambda> at 0xb7bf75ec>
>>>>
>
> So just remove the parentheses and you'll be fine.
No, you change the function signature in the process.
f = lambda (a, b): a*b
is equivalent to
def f((a, b)): # double parens
return a*b
and called as f(arg) where arg is an iterable with two items.
In 3.0 it has to be rewritten as
def f(ab):
a, b = ab
return a*b
i. e. it needs a statement and an expression and is therefore no longer
suitable for a lambda.
Peter
--
http://mail.python.org/mailman/listinfo/python-list
