Simplify dictionary update

[emorozov]

Issue description or question

I often see the code like:

def foo(d: dict) -> None:
   d.update({'request': HttpRequest()})
   frobnicate(d)

Here .update can and should be replaced with:

d['request'] = HttpRequest()

Sourcery Version

0.9.5

Code editor or IDE name and version

Pycharm v2021.2.2

OS name and version

Arch Linux (Linux lenovo 5.14.7-arch1-1 #1 SMP PREEMPT Wed, 22 Sep 2021 21:35:11 +0000 x86_64 GNU/Linux)

[Hellebore]

yeah this looks like a nice little improvement

[ruancomelli]

Be careful with multiple keys:

from typing import Dict

d1: Dict[str, int] = {'a': 0, 'b': 10}
d1.update({'a': d1['b'], 'b': d1['a']})
print(d1) # {'a': 10, 'b': 0}

d2: Dict[str, int] = {'a': 0, 'b': 10}
d2['a'] = d2['b']
d2['b'] = d2['a']
print(d2) # {'a': 10, 'b': 10}

Another possible refactoring here is when the "update_dict" keys are all str, in which case we can update the original dict using keyword arguments:

d1: Dict[str, int] = {'a': 0, 'b': 10}
d1.update({'a': d1['b'], 'b': d1['a']})
print(d1) # {'a': 10, 'b': 0}

d2: Dict[str, int] = {'a': 0, 'b': 10}
d2.update(a=d2['b'], b=d2['a'])
print(d2) # {'a': 10, 'b': 0}

[Hellebore]

Added in 0.9.6