Confusing error message: lambda walruses

[Peter J. Holzer]

On 2021-10-03 10:39:38 +1100, Chris Angelico wrote:
> # Oh, and it doesn't actually assign anything.
> >>> def f(n):
> ...     return (lambda: (n := 1)), (lambda: n)
> ...
> >>> g, h = f(5)
> >>> h()
> 5
> >>> g()
> 1
> >>> h()
> 5

I thought about that one a bit more and I think that the lambda is
creating a new scope, just like a regular function would, so it is
assigning to its own private «n», not the «n» in «f(n)».

https://docs.python.org/3/reference/expressions.html#grammar-token-lambda-expr
doesn't mention scope explicitely, but

|    The unnamed object behaves like a function object defined with:
|
|    def <lambda>(parameters):
|        return expression

implies to me that it should create a new scope because a nested function
defined with «def» would do that, too.

        hp

-- 
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp at hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"
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