On 14/09/18 10:29, Chris Angelico wrote:
On Fri, Sep 14, 2018 at 5:25 PM, Antoon Pardon <antoon.par...@vub.be> wrote:
On 13-09-18 14:29, Chris Angelico wrote:
"Preferred" doesn't exclude the possibility that alternatives are
needed, though. For example, good luck making decimal.Decimal contexts
work correctly without the help of thread-locals - there MIGHT be a
way to do it, but even if there is, it sure won't be pretty.
Can you elaborate on that. Suppose I have two threads, one in which I need
a precision of 3 and the other in which I need a precision of 7. In what
circumstances is it needed to use threads-locals to accomplish this and
how do I accomplish this?
If I want my decimal code be usable with threads, how should I write it?
Let's say both of those threads call the same function, which does this:
def f(x, y):
return x * 3 + y / 4
You can't pass a context as a parameter, so you have to set the
context externally. Which is done thus:
https://docs.python.org/3/library/decimal.html#decimal.setcontext
Note that this sets it *for the current thread*.
ChrisA
Ideally use a context manager to manage your context:
https://docs.python.org/3/library/decimal.html#decimal.localcontext
-- Thomas
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