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This article introduces how to use the set function in Python, the content is very detailed, interested friends can refer to, hope to be helpful to you.

The set collection function is mainly used to remove repetition:

For example, if a list has multiple duplicate values, you can get rid of it with set

> l = [1, 2, 3, 4, 5, 4, 4, 3, 21]

> > >

> > l

[1, 2, 3, 4, 5, 4, 3, 21]

> > >

> > >

Set (l)

Set ([1,2,3,4,5,21])

> > >

Set can do intersection, union and subtraction.

Addition, deletion and modification of set

Zeng: > a = set ([1Jing 2Jing 3Jing 4])

> > a

Set ([1,2,3,4])

> > >

> a.add ('alex')

> > a

Set ([1,2,3,4, 'alex'])

Delete: > a.remove ('alex')

> > a

Set ([1,2,3,4])

> > >

Add multiple items: > b = set ([1, 2, 7, 8])

> > b

Set ([8,1,2,7])

> > a.update (b)

> > a

Set ([1,2,3,4,7,8])

Determine whether b is included in a

> > a

Set ([1,2,3,4,7,8])

> > b

Set ([8,1,2,7])

> > >

> > b.issubset (a)

True

The "unordered" set in python is relative to other set implemented with balanced binary trees, such as set in C++ using red-black trees and orderedset in python.

Set access operations based on balanced binary tree are all O (lgn) time, but because of the characteristics of binary search tree, it is easy to find the precursor and successor nodes of any node, so it can be regarded as "orderly".

The set in python is implemented based on hash table, and the access time can be regarded as O (1), but there is no way to efficiently complete sequence-related operations (such as finding precursors and successors, maximum and minimum values, etc.), so it is considered to be "unordered".

On how to use the set function in Python to share here, I hope the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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