Python notes (3) important points of knowledge

1. For an immutable object, any method that invokes the object itself does not alter the contents of the object itself. Instead, these methods create a new object and return it, ensuring that the immutable object itself is always immutable. STR is an immutable object, and list is a mutable object, and a tuple is an immutable object

2. Set and Dict, is a set of key sets. Since key cannot be duplicated, there is no duplicate key in it. The only difference between set and dict is that the corresponding value is not stored. It is important to choose an immutable object as key, and the most commonly used key is a string.

Python notes (3) important points of knowledge