"with" statement

[arshajii]

with can be transformed into try...finally at the compiler level:

with <expr> as v:
    <block>

can be converted to:

# new scope so `v` is not accessible outside `with` body
v = <expr>
v.__enter__()
try:
    <block>
finally:
    v.__exit__()

---

withs with multiple clauses can be converted to single-clause nested withs:

with <e1> as v1, <e2> as v2, ..., <eN> as vN:
    <block>

becomes

with <e1> as v1:
    with <e2> as v2:
        ...
            with <eN> as vN:
                <block>

before applying the preceding transformation.

[arshajii]

Python's __exit__() also takes exception info -- we can think about how/if we want to support that as well.

[inumanag]

Real pythonic with requires nested try statements:
https://stackoverflow.com/questions/26096435/is-python-with-statement-exactly-equivalent-to-a-try-except-finally-bloc

I'd prefer postponing this until we have working nested try statements

[arshajii]

Nested try-except is #34.