PyMutator

Mutate nested Python objects using a method inspired by SolidJS's setState function for updating stores.

https://www.solidjs.com/docs/latest/api#updating-stores

Examples

update lists by index

>>> from pymutator import mutate
>>> mutate([1, 2, 3, 4, 5], 3, 'D')
[1, 2, 3, 'D', 5]

update lists by list of indices

>>> mutate([1, 2, 3, 4, 5], [1, 3], 'D')
[1, 'D', 3, 'D', 5]

update lists by filter predicate

>>> mutate([1, 2, 3, 4, 5], lambda i: i%2, 'odd')
['odd', 2, 'odd', 4, 'odd']

update list with computed value

>>> mutate([1, 2, 3, 4, 5], 3, lambda i: f'D{i}')
[1, 2, 3, 'D4', 5]

update dict

>>> mutate({'a': 1, 'b': 2, 'c': 3}, 'b', 'B')
{'a': 1, 'b': 'B', 'c': 3}

>>> mutate({'a': 1, 'b': 2, 'c': 3}, b='B')
{'a': 1, 'b': 'B', 'c': 3}

>>> mutate({'a': 1, 'b': 2, 'c': 3}, {'b': 'B'})
{'a': 1, 'b': 'B', 'c': 3}

>>> mutate({'a': 1, 'b': 2, 'c': 3}, ['b', 'x'], 'B')
{'a': 1, 'b': 'B', 'c': 3, 'x': 'B'}

update dict with filter predicate

>>> mutate({'a': 1, 'b': 2, 'c': 3}, lambda i: i%2, 'odd')
{'a': 'odd', 'b': 2, 'c': 'odd'}

update dict with computed value

>>> mutate({'a': 1, 'b': 2, 'c': 3}, 'b', lambda i: f'B{i}')
{'a': 1, 'b': 'B2', 'c': 3}

update object

>>> class O:
...     def __init__(self): self.a = 1
>>> o = O()
>>> mutate(o, 'a', 2) and o.a
2

>>> mutate(o, a=3) and o.a
3

>>> mutate(o, {'a': 4}) and o.a
4

>>> mutate(o, 'a', lambda i: i+1) and o.a
5

updating nested objects

>>> store = {
...    'todos': [
...            {'task': 'Finish work', 'completed': False},
...            {'task': 'Go grocery shopping', 'completed': False},
...            {'task': 'Make dinner', 'completed': False},
...        ]
...    }

>>> mutate(store, 'todos', [0, 2], 'completed', True)
{'todos': [{'task': 'Finish work', 'completed': True}, {'task': 'Go grocery shopping', 'completed': False}, {'task': 'Make dinner', 'completed': True}]}

>>> mutate(store, 'todos', lambda todo: todo['completed'],
...        'task', lambda t: t + '!')
{'todos': [{'task': 'Finish work!', 'completed': True}, {'task': 'Go grocery shopping', 'completed': False}, {'task': 'Make dinner!', 'completed': True}]}

Running tests

$ pytest