Python Set intersection

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本文详细介绍了Python中集合的交集方法intersection()的使用方法，包括语法、参数说明及返回值解析。通过多个实例演示了如何求两个或多个集合的交集，并展示了使用&运算符实现相同功能的方法。

Python Set intersection()

转自：https://www.programiz.com/python-programming/methods/set/intersection

The intersection() method returns a new set with elements that are common to all sets.

The intersection of two or more sets is the set of elements which are common to all sets. For example:

A = {1, 2, 3, 4}
B = {2, 3, 4,  9}
C = {2, 4, 9 10}

Then,
A∩B = B∩A ={2, 3, 4}
A∩C = C∩A ={2, 4}
B∩C = C∩B ={2, 4, 9}

A∩B∩C = {2, 4}

Intersection of Three Sets

The syntax of intersection() in Python is:

A.intersection(*other_sets)

intersection() Parameters

The intersection() allows arbitrary number of arguments (sets).

Note: * is not part of the syntax. It is used to indicate that the method allows arbitrary number of arguments.

Return Value from Intersection()

The intersection() method returns the intersection of set A with all the sets (passed as argument).

If argument is not passed to intersection(), it returns a shallow copy the set (A).

Example 1: How intersection() works?

A = {2, 3, 5, 4}

B = {2, 5, 100}

C = {2, 3, 8, 9, 10}

print(B.intersection(A))

print(B.intersection(C))

print(A.intersection(C))

print(C.intersection(A, B))

Run

When you run the program, the output will be:

{2, 5}
{2}
{2, 3}
{2}

More Examples

A = {100, 7, 8}

B = {200, 4, 5}

C = {300, 2, 3}

D = {100, 200, 300}

print(A.intersection(D))

print(B.intersection(D))

print(C.intersection(D))

print(A.intersection(B, C, D))

Run

When you run the program, the output will be:

{100}
{200}
{300}
set()

You can also find the intersection of sets using & operator

Example 3: Set Intersection Using & operator

A = {100, 7, 8}

B = {200, 4, 5}

C = {300, 2, 3, 7}

D = {100, 200, 300}

print(A & C)

print(A & D)

print(A & C & D)

print(A & B & C & D)

Run

When you run the program, the output will be:

{7}
{100}
set()
set()