On Tue, Jun 29, 2021 at 7:51 AM Max Shouman <shouman.max@gmail.com> wrote:
This is more of a syntactic sugar than an actual new feature, but... Exactly, 'but' is the idea: a special keyword to be used in for statements to exclude values from the iterable.
E.g., when iterating over a generator:
for i in range(0, 10) but (2, 8): would implicitly create a new generator comprehensively, as in: for i in (j for j in range(0, 10) if j not in [2, 8]):
It might not add such a feature to justify the definition of a but_stmt in python.gram, but it's fully compliant with Python's philosophy of concise, clear and elegant code.
#road to a programming natural language (jk)
Python currently has 35 keywords. To justify a 36th, there needs to be a *lot* of benefit. Instead, perhaps it'd be worth devising your own range() type which is capable of subtraction? _range = range class range: def __init__(self, *args, exclude=()): self.basis = _range(*args) self.excludes = exclude def __sub__(self, other): return type(self)(r.start, r.stop, r.step, excludes=self.exclude + other) def __iter__(self): for val in self.basis: if val not in self.excludes: yield val Then you can write this: for i in range(0, 10) - (2, 8): ... Tada! No new keyword needed, and it reads better than "but" does ("except for" would be how English would normally write that). ChrisA