数据类型的内置方法:集合

目录

数据类型的内置方法:集合

作用

  • 用于关系运算的集合体,由于集合内的元素无序且集合元素不可重复,因此集合可以去重,但是去重后的集合会打乱原来元素的顺序。
  • 一个值or多个值:多个值,且值为不可变数据类型
  • 有序or无序:无序
  • 可变or不可变:可变

定义

  • {} 内用逗号分隔开多个元素,每个元素必须是不可变类型。
s = {1,2,1,'a'}  # s = set({1,2,'a'})
print(s)  # {1,2,'a'}

优先掌握的内置方法

1:len 长度

s = {1,2,3}
print(len(s))  # 3

2:成员运算 in 和 not in

s = {1,3,5,'a'}
print('a' in s)  # True
print('a' not in s)  #False

3:| 并集(union)

pythoners = {'jason','nick','egon','jin'}
linuxers = {'kevin','nick','egon'}
print(pythoners | linuxers)  
# {'nick', 'jason', 'jin', 'kevin', 'egon'}

4:& 交集(intersection)

pythoners = {'jason','nick','egon','jin'}
linuxers = {'kevin','nick','egon'}
print(pythoners & linuxers)
# {'egon', 'nick'}

5:- 差集(difference)

pythoners = {'jason','nick','egon','jin'}
linuxers = {'kevin','nick','egon'}
print(pythoners - linuxers)
# {'jin', 'jason'}

6:^ 对称差集(symmetric_difference)

pythoners = {'jason','nick','egon','jin'}
linuxers = {'kevin','nick','egon'}
print(pythoners ^ linuxers)
# {'jason', 'kevin', 'jin'}

7: ==

pythoners = {'jason','nick','egon'}
linuxers = {'jason','nick','egon'}
print(pythoners == linuxers)
#  False

8:父集 >,>=,(issuperset)

pythoners = {'jason','nick','egon','jin'}
linuxers = {'nick','egon'}
print(pythoners > linuxers)  # True
print(pythoners >= linuxers)  # True

9:子集 <,<=,(issubset)

pythoners = {'jason','nick','egon','jin'}
linuxers = {'nick','egon'}
print(linuxers < pythoners)  # True
print(linuxers <= pythoners)  #True
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