[Raymond Hettinger]
> The sin() example is correct. The precision is changed and restored in
> the current context.
I got that eventually. :-)
> However, for a general purpose wrapper, it is preferable to make a
> context copy and then restore the context after the enclosed is run.
> That guards against the enclosed block making any unexpected context
> changes.
(Although if people get in the habit of using the provided wrappers
and the do-statement, there won't be any unexpected changes.)
> Also, since the wrapper is intended to work like a try/finally, it will
> make sure the context gets restored even if an exception is raised at
> some unexpected point in the middle of the computation.
Yes, that's the point of the do-statement. :-
Anyway, perhaps we should provide this most general template:
@do_template
def with_decimal_context():
oldctx = decimal.getcontext()
newctx = oldctx.copy()
decimal.setcontext(newctx)
yield newctx
decimal.setcontext(oldctx)
To be used like this:
do with_decimal_context() as ctx:
ctx.prec += 2
# change other settings
# algorithm goes here
--
--Guido van Rossum (home page: http://www.python.org/~guido/)
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