copy.deepcopy(UnitRegistry())

[crusaderky]

Closes #856

Allow creating an independent copy of a UnitRegistry through deepcopy().
Also introduce several speedups in UnitsContainer and ParserHelper.

[crusaderky]

copy.deepcopy misbehaves in case of dynamic class definition, such as that performed by build_unit_class:

>>> def gen_C():
...     class C:
...         pass
...     return C

>>> C1 = gen_C()
>>> C2 = copy.deepcopy(C1)
>>> C2 is C1
True

[crusaderky]

...aaand done :)

This gives some performance benefit compared to re-initialising everything from the beginning:

%timeit pint.UnitRegistry()
135 ms ± 2.31 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)

ureg = pint.UnitRegistry()
%timeit copy.deepcopy(ureg)
42.7 ms ± 799 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

[crusaderky]

@hgrecco this is ready for review and merge

[hgrecco]

Great. I would like a second opinion as this is a rather large change. Maybe @andrewgsavage or @jondoesntgit can take also a look.

[crusaderky]

@hgrecco @andrewgsavage @jondoesntgit ping - any observations before this can be merged?

[jondoesntgit]

I don't have any observations. This is a bug that I've never had to worry about in my code.

[andrewgsavage]

Me neither

[hgrecco]

bors r+

[bors]

Build succeeded

• continuous-integration/travis-ci/push

[crusaderky]

Thank you!