On Wed, Jul 25, 2018 at 10:29 PM Chris Angelico <ros...@gmail.com> wrote:
> food = spam?.eggs?.bacon > > can be rewritten as > > _tmp = spam > if _tmp is not None: > _tmp = _tmp.eggs > if _tmp is not None: > _tmp = _tmp.bacon > food = _tmp > Yes, that looks right. Well, you need a `del _tmp` at the end; but it's almost right. My point was that both you and Nicholas Chammas failed to recognize that the other translation was wrong... I recognize it does something "kinda similar." But the semantics of the operators are just plain hard to grok, even by their strongest advocates. I can write lots of things that are "mostly correct" already in Python. Most easily, I can write: try: food = spam.eggs.bacon except: food = None That does what is actually needed about 95% of the time. It's also clear and easy to understand. It is *actually impossible* to > perfectly represent short-circuiting semantics in Python! It's INCREDIBLY EASY to represent short-circuiting semantics in Python! What on earth are you talking about? That's what the if/elif/else blocks do. And before you go "well that proves my point, this suggestion is bad", let's > apply the same test to a few other pieces of syntax. Rewrite the > following statements without using the syntactic feature named in the > comment: > This is childishly simple: > # 1) Decorators > @deco > def func(): > ... > def func(): ... func = deco(func) OK, this one is harder. The "mostly correct" version is easy. But the actual full version is nuanced (see https://www.python.org/dev/peps/pep-0380/ for details). # 2) "yield from" > def chain(*iters): > for iter in iters: > yield from iter > # The simple approximation: for iter in iters: for _ in iter: yield iter > # 3) and the big one: generator expressions > # yes, I'm deliberately using x multiple ways here > def f(x): return x*x > x = range(10) > x = (f(x) for x in x if x % 2) > I'm not going to bother with that. I'd fire anyone who wrote it, after code review. Minus the abuse of names, it's just: def gen(xs): for x in xs: if x % 2: yield f(x) x = gen(xs) -- Keeping medicines from the bloodstreams of the sick; food from the bellies of the hungry; books from the hands of the uneducated; technology from the underdeveloped; and putting advocates of freedom in prisons. Intellectual property is to the 21st century what the slave trade was to the 16th.
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