On Wed, Jul 25, 2018 at 10:29 PM Chris Angelico <rosuav@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.