On Sun, Oct 31, 2021 at 03:10:56PM +1100, Chris Angelico wrote:
> (Side point: The current reference implementation allows assignment
> expressions inside default argument expressions, mainly because I
> didn't go to the effort of blocking them. But if you ever ACTUALLY do
> this, then..... *wat*)
Why? The result is well-defined. It might not be *good* code, but let's
not be overzealous with banning legal code just because it is bad :-)
That's the job of linters and code reviews.
In an early bound default, the walrus operator binds to a name in the
scope the expression is evaluated in, i.e. the surrounding scope. So a
top level function with a walrus:
string = "hello"
def func(spam=(a:=len(string)), eggs=2**a):
return (spam, eggs)
binds to a global variable `a`.
Similarly, a walrus inside a late bound default should bind to a local
variable. The walrus doesn't get executed until the function namespace
is up and running, and the walrus is a binding operation, so it should
count as a local variable.
--
Steve
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