immerframe 0.0.3

creates the next immutable object by simply modifying the current one

immerframe

Create the next immutable object by simply modifying the current one

This is a Python port of immer.

pip install immerframe

Want to do a deep update on a Python data structure without mutating it? No problem:

from immerframe import Proxy, produce

Ant = namedtuple('Ant', 'age')
nested = {
    'foo': [
        Ant(age=2),
        'bar',
    ],
}

proxy = Proxy()
proxy['foo'][0].age += 1
proxy['foo'].pop()
proxy['qux'] = 99

new_nested = produce(proxy, nested)

new_nested will now equal

{
    'foo': [
        Ant(age=3),
    ],
    'qux': 99,
}

while nested will remain unchanged.

"What about my typing?"

from typing import cast

Cat = namedtuple('Cat', 'name')

proxy = cast(Cat, Proxy())
# continue as before but with autocomplete and type checking!
proxy.name = 'Felix'

immerframe uses structural sharing, so should be efficient in most cases:

d = {'foo': 1}
l = [d]

proxy = Proxy()
proxy.append(100)
new_l = produce(proxy, l)
assert new_l == [d, 100]
assert new_l[0] is d

immerframe supports:

• dicts
• lists
• sets
• tupless
• namedtupless
• attrss

Lens

immerframe comes with a Lens class to help with path reuse:

d = {'foo': [1, 2, 3, 4]}

lens = Lens(Proxy()['foo'][1])

new_d = lens.set(d, 100)
assert new_d == {'foo': [1, 100, 3, 4]}
assert d == {'foo': [1, 2, 3, 4]}
assert lens.get(d) == 2

Plugins:

immerframe currently has an attrs plugin, registering plugins is pretty easy, just mutate the immerframe.plugins list (see here for the structure of the existing attr plugin).