Confusing error message: lambda walruses
Peter J. Holzer
hjp-python at hjp.at
Sun Oct 3 08:02:18 EDT 2021
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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