How to check if a key exists in a dictionary?

What is the purpose of __slots__ in Python? Especially regarding when to use it and when not to?

TLDR:

The special attribute __slots__ allows you to explicitly specify which instance attributes you expect from instances of your object, with the expected results:

1. faster access to attributes.
2. memory savings.

Space is saved because

1. References are stored to the slot values instead of in __dict__

2. Prevents creation of __dict__ and __weakref__ if parent classes prevent them and you declare __slots__.

Brief warnings

In the inheritance tree, declar