[Python-ideas] adding an __exec__ method to context managers?

[Carl Johnson]

Ben Finney:

> What is insufficiently readable about::
>
>  def foo(spam):
>      process_wibble(spam)
>      process_wobble(spam)
>      return process_warble(spam)
>
>  bar(foo)

The problem with that is in 3 or 4 months someone will come back to
Python-ideas with another theory of how to replace it.

More seriously, it puts things out of order. If you had to write for-loops as

def loop(item):
   process(item), etc.

for(loop, iterator)

it would be patently obvious that the for(loop, iterator) belongs at
the top, not the bottom, so that you know *what* is being iterated
before you find out *how* it's being iterated. For that matter, Python
has changed the perfectly sensible:

def method(cls):
   stuff()

method = classmethod(method)

to

@classmethod
def method(cls):
   stuff()

Why? Because it's more readable to have the decorator up top, so you
know what kind of function/method to expect.

So, in this particular case, I think it's more readable to have the
conditions at the top instead of the bottom.

It's very natural when something that starts as

 for i in range(100):
    dostuff1(i) # thread safe function
    dostuff2(i) # not thread safe function

becomes

with parallelize(range(100)) as i:
    dostuff1(i) # thread safe function
    dostuff2(i) # not thread safe function

(or some other way of writing the condition at the top instead of,
such as a decorator etc.) instead of

def f(i):
    dostuff1(i) # thread safe function
    dostuff2(i) # not thread safe function

parallelize(f, range(100))

with the loop condition at the bottom.

For whatever reason, people find putting the conditions out of order
onerous, and Python-ideas won't be free of periodic interruptions
until there someway to conditions into their mental order.

— Carl