Python Learning 12--Collection

1. Features of the collection
1). Unique. That is, the elements inside cannot be duplicated, but the statement does not give an error, but he will
Duplicate element to delete one.
2). Index acquisition is not supported. That is, the elements in the collection are unordered.
2. Creation of collections
1). Enclose some elements directly in curly braces. Example: num={1,2,3}
2). Created with the set () function. Set1=set ([+]), then set1={1,2,3}
3. Accessing values within a collection
1). Access by
2). Determine whether the presence is in the collection by in, not.
4. Adding, removing elements
Add (), remove ();
5. Immutable Collections
Frozenset (), used in a sense similar to set, is used to create an immutable collection where an element cannot be added or deleted.

Python Learning 12--Collection