For function definitions, the introduction of `*` to mark keyword-only
parameters was consistent with existing syntax in a sense that `def
foo(*args, bar)` had `args` consume all positional arguments, so `bar`
can only be passed via keyword. Now using `def foo(*, bar)` just omits
the positional argument part, but leaves `bar` unchanged.
However for function calls you can have positional arguments following
argument unpacking:
def foo(a, b):
print(a, b)
a, b = 2, 1
foo(*[], b, a) # prints "1 2"
Now omitting the unpacking part would change the meaning of what
follows, namely that it is to be interpreted as keyword arguments:
foo(*, b, a) # prints "2 1"
Sure you could argue that a lonely `*` in a function call has to have
some effect, so it must change what comes after it, but this slight
asymmetry between definition and calling of a function could be confusing.
On 16.04.20 19:54, Alex Hall wrote:
I beg to differ. I do find "def foo(a, *, b)" gets in the way of
readability.
--
Rhodri James *-* Kynesim Ltd
In what way?
In any case, focusing on the calling syntax being proposed, is there
anything unreadable about:
foo(a, *, b)
compared to
foo(a, b=b)
? I think in the proposed syntax it's quite easy to understand that
we're passing arguments 'a' and 'b' even if we have no idea what the
'*' means, and it's small enough that it's fairly easy to mentally
filter out.
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