Oscar Benjamin writes:
> On Sun, 7 Feb 2021 at 23:55, Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
> > On 8/02/21 6:59 am, Christopher Barker wrote:
> > > I find myself
> > I often write
> My preferred option is
There's ALWAYS more than one way to do it! :-)
I'm not a fan of the proposed new syntax. A big issue for me is that
"with" doesn't commute with "if". That is Chris will write
with open('file') as f:
lines = r.readlines()
for line in lines:
process(line)
instead of
with open('file') as f:
for line in f:
process(line)
but AFAICS the proposed syntax doesn't help by itself:
for line in (what?) with open('file'):
process(line)
and
for line in f with open('file') as f:
process(line)
will be horrible with any more complicated context manager constructor
IMO, YMMV. Note that I'm assuming a similar facility for 'for', for
convenience of exposition. Nobody has proposed it yet, I think, just
mentioned it. I guess you could do as Jonathan's code does:
f = open('file', and, many, more, arguments)
for line in f with f:
process(line)
but I'm not impressed by that syntax. In the case in Jonathan's post,
if stamp.expired():
with stamp:
[code]
is TRT, but I wonder how often it is, compared to cases where
with stamp:
if stamp.expired():
[code]
DTRTs. Notice that once you combine them into a single statement, you
can choose either semantics, which is a bug magnet.
Of course you could try allowing both "if ... with ..." and "with
... if ..." with the evident semantics, but "with thing if" already
has a meaning ("thing if" introduces a conditional expression).
Although the PEG parser can presumably handle it, I'm not a fan of
parsing "with thing if" as a combined with/if statement if the else
arm is missing, and otherwise as a with/conditional expression
statement.
Bottom line: IMO this syntax probably should be limited to the
particular case where there's a context manager that doesn't need to
be referred to in the block, and the nesting is if = outer, with =
inner. I don't think that's enough to justify new syntax, merely to
save one level of indentation that can be saved in a large number of
ways that probably cover most of the use cases.
Steve
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