集合类型内置方法

目录

* set(掌握) <https://www.cnblogs.com/nickchen121/p/10744169.html#set掌握>
* 优先掌握(*****) <https://www.cnblogs.com/nickchen121/p/10744169.html#优先掌握>
* 需要掌握(****) <https://www.cnblogs.com/nickchen121/p/10744169.html#需要掌握>
* 练习(掌握) <https://www.cnblogs.com/nickchen121/p/10744169.html#练习掌握>
set(掌握)

集合可以理解成一个集合体，学习Python的学生可以是一个集合体；学习Linux的学生可以是一个集合体。
pythoners = ['jason', 'nick', 'tank', 'sean'] linuxers = ['nick', 'egon',
'kevin'] # 即报名pythoners又报名linux的学生 py_li_list = [] for stu in pythoners: if stu
in linuxers: py_li_list.append(stu) print(f"pythoners and linuxers:
{py_li_list}") pythoners and linuxers: ['nick']


上述的列表方式求两个集合体的关系运算非常复杂，因此有了我们的集合数据类型。

1.用途：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。

2.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(f"s: {s}") s: {1, 2, 'a'} s =
{1, 2, 1, 'a', 'c'} for i in s: print(i) 1 2 c a s = set('hello') print(f"s:
{s}") s: {'e', 'o', 'h', 'l'}
3.常用操作+内置方法：常用操作和内置方法分为优先掌握（今天必须得记住）、需要掌握（一周内记住）两个部分。

优先掌握(*****)

1.长度len
# set之长度len s = {1, 2, 'a'} print(f"len(s): {len(s)}") len(s): 3
2.成员运算in和not in
# set之成员运算in和not in s = {1, 2, 'a'} print(f"1 in s: {1 in s}") 1 in s: True




3.|并集
# str之|并集 pythoners = {'jason', 'nick', 'tank', 'sean'} linuxers = {'nick',
'egon', 'kevin'} print(f"pythoners|linuxers: {pythoners|linuxers}")
print(f"pythoners.union(linuxers): {pythoners.union(linuxers)}")
pythoners|linuxers: {'egon', 'tank', 'kevin', 'jason', 'nick', 'sean'}
pythoners.union(linuxers): {'egon', 'tank', 'kevin', 'jason', 'nick', 'sean'}
4.&交集
# str之&交集 pythoners = {'jason', 'nick', 'tank', 'sean'} linuxers = {'nick',
'egon', 'kevin'} print(f"pythoners&linuxers: {pythoners&linuxers}")
print(f"pythoners.intersection(linuxers): {pythoners.intersection(linuxers)}")
pythoners&linuxers: {'nick'} pythoners.intersection(linuxers): {'nick'}
5.-差集
# str之-差集 pythoners = {'jason', 'nick', 'tank', 'sean'} linuxers = {'nick',
'egon', 'kevin'} print(f"pythoners-linuxers: {pythoners-linuxers}")
print(f"pythoners.difference(linuxers): {pythoners.difference(linuxers)}")
pythoners-linuxers: {'tank', 'jason', 'sean'} pythoners.difference(linuxers):
{'tank', 'jason', 'sean'}
6.^对称差集
# str之^对称差集 pythoners = {'jason', 'nick', 'tank', 'sean'} linuxers = {'nick',
'egon', 'kevin'} print(f"pythoners^linuxers: {pythoners^linuxers}") print(
f"pythoners.symmetric_difference(linuxers):
{pythoners.symmetric_difference(linuxers)}") pythoners^linuxers: {'egon',
'tank', 'kevin', 'jason', 'sean'} pythoners.symmetric_difference(linuxers):
{'egon', 'tank', 'kevin', 'jason', 'sean'}
7.==
# str之== pythoners = {'jason', 'nick', 'tank', 'sean'} linuxers = {'nick',
'egon', 'kevin'} javers = {'nick', 'egon', 'kevin'}
print(f"pythoners==linuxers: {pythoners==linuxers}") print(f"javers==linuxers:
{javers==linuxers}") pythoners==linuxers: False javers==linuxers: True
8.父集：>、>=
# str之父集：>、>= pythoners = {'jason', 'nick', 'tank', 'sean'} linuxers =
{'nick', 'egon', 'kevin'} javaers = {'jason', 'nick'}
print(f"pythoners>linuxers: {pythoners>linuxers}") print(f"pythoners>=linuxers:
{pythoners>=linuxers}") print(f"pythoners>=javaers: {pythoners>=javaers}")
print(f"pythoners.issuperset(javaers): {pythoners.issuperset(javaers)}")
pythoners>linuxers: False pythoners>=linuxers: False pythoners>=javaers: True
pythoners.issuperset(javaers): True
9.子集：<、<=
# str之子集：<、<= pythoners = {'jason', 'nick', 'tank', 'sean'} linuxers =
{'nick', 'egon', 'kevin'} javaers = {'jason', 'nick'}
print(f"pythoners<linuxers: {pythoners<linuxers}") print(f"pythoners<=linuxers:
{pythoners<=linuxers}") print(f"javaers.issubset(javaers):
{javaers.issubset(javaers)}") pythoners<linuxers: False pythoners<=linuxers:
False javaers.issubset(javaers): True
需要掌握(****)

1.add()
# set之add() s = {1, 2, 'a'} s.add(3) print(s) {1, 2, 3, 'a'}
2.remove()
# set之remove() s = {1, 2, 'a'} s.remove(1) print(s) {2, 'a'}
3.difference_update()
# str之difference_update() pythoners = {'jason', 'nick', 'tank', 'sean'}
linuxers = {'nick', 'egon', 'kevin'} pythoners.difference_update(linuxers)
print(f"pythoners.difference_update(linuxers): {pythoners}")
pythoners.difference_update(linuxers): {'tank', 'jason', 'sean'}
4.discard()
# set之discard() s = {1, 2, 'a'} # s.remove(3) # 报错 s.discard(3) print(s) {1,
2, 'a'}
5.isdisjoint()
# set之isdisjoint()，集合没有共同的部分返回True，否则返回False pythoners = {'jason', 'nick',
'tank', 'sean'} linuxers = {'nick', 'egon', 'kevin'}
pythoners.isdisjoint(linuxers) print(f"pythoners.isdisjoint(linuxers):
{pythoners.isdisjoint(linuxers)}") pythoners.isdisjoint(linuxers): False
练习(掌握)

有如下列表，列表元素为不可hash类型，去重，得到新列表，且新列表一定要保持列表原来的顺序
stu_info_list = [ {'name':'nick','age':19,'sex':'male'},
{'name':'egon','age':18,'sex':'male'}, {'name':'tank','age':20,'sex':'female'},
{'name':'tank','age':20,'sex':'female'}, {'name':'egon','age':18,'sex':'male'},
]

stu_info_list = [ {'name': 'nick', 'age': 19, 'sex': 'male'}, {'name': 'egon',
'age': 18, 'sex': 'male'}, {'name': 'tank', 'age': 20, 'sex': 'female'},
{'name': 'tank', 'age': 20, 'sex': 'female'}, {'name': 'egon', 'age': 18,
'sex': 'male'}, ] new_stu_info_list = [] for stu_info in stu_info_list: if
stu_info not in new_stu_info_list: new_stu_info_list.append(stu_info) for
new_stu_info in new_stu_info_list: print(new_stu_info) {'name': 'nick', 'age':
19, 'sex': 'male'} {'name': 'egon', 'age': 18, 'sex': 'male'} {'name': 'tank',
'age': 20, 'sex': 'female'}
4.存一个值or多个值：多个值，且值为不可变类型。

5.有序or无序：无序
s = {1, 2, 'a'} print(f'first:{id(s)}') s.add(3) print(f'second:{id(s)}')
first:4481677128 second:4481677128
6.可变or不可变：可变数据类型

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