I hear where you're coming from but I really don't think we should do this. If you don't have the right expectation already it's hard to guess what it means. I would much rather spend effort on a proper matching statement.
On Thu, Apr 12, 2018 at 2:54 AM, Serhiy Storchaka <storch...@gmail.com> wrote: > Yet one crazy idea. What if allow default values for targets in > multi-target assignment? > > >>> (a, b=0) = (1, 2) > >>> a, b > (1, 2) > >>> (a, b=0) = (1,) > >>> a, b > (1, 0) > >>> (a, b=0) = () > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > ValueError: not enough values to unpack (expected at least 1, got 0) > >>> (a, b=0) = (1, 2, 3) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > ValueError: too many values to unpack (expected at most 2) > > Currently you need either explicitly check the length of the right-hand > part (if it is a sequence and not an arbitrary iterator), > > if len(c) == 1: > a, = c > b = 0 > elif len(c) == 2: > a, b = c > else: > raise TypeError > > or use an intermediate function: > > def f(a, b=0): > return a, b > a, b = f(*c) > > The latter can be written as an ugly one-liner: > > a, b = (lambda a, b=0: (a, b))(*c) > > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ > -- --Guido van Rossum (python.org/~guido)
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