On 8/11/19 13:00, Chris Angelico wrote:
> On Fri, Nov 8, 2019 at 10:57 PM Antoon Pardon <antoon.par...@vub.be> wrote:
>> On 7/11/19 18:10, Stephen Waldron wrote:
>>> What I'm aiming for is the ability to, within a function call, pass a suite
>>> that would be there automatically defined by the compiler/interpreter.
>>> Another comment did mention lambda functions, which does to some degree
>>> provide that capability, but is restricted to well, lambda functions (only
>>> expressions, not statements).
>> I don't think those restrictions are that limiting. Certainly not since
>> python3.8 and python acquired an assigment operator. And you should also
>> note that a list is an expression. So we could do something like the
>> following.
>>
> If you're implying that you can rewrite any function using lambda and
> a list of expressions, then no, the ":=" operator won't help you:
>
>>>> (lambda: x := 1)
> File "<stdin>", line 1
> SyntaxError: cannot use named assignment with lambda
Well I haven't had the time to install python3.8 myself but this is what
I read in the PEP
* Unparenthesized assignment expressions are prohibited in lambda
functions. Example:
(lambda: x := 1) # INVALID
lambda: (x := 1) # Valid, but unlikely to be useful
(x := lambda: 1) # Valid
lambda line: (m := re.match(pattern, line)) and m.group(1) # Valid
This allows lambda to always bind less tightly than :=; having a
name binding at the top level inside a lambda function is unlikely
to be of value, as there is no way to make use of it. In cases where
the name will be used more than once, the expression is likely to
need parenthesizing anyway, so this prohibition will rarely affect code.
So it seems you just forgot to use the parenthesis.
--
Antoon Pardon
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