python基础-20集合类型内置方法

集合类型内置方法(set)

集合能够理解成一个集合体，学习Python的学生能够是一个集合体；学习Linux的学生能够是一个集合体。

pythoners = ['nash', 'langyigang', 'fujiancheng', 'jinyi']
linuxers = ['nash', 'yankeming', 'zhaoyanrun']

# 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}")

上述的列表方式求两个集合体的关系运算很是复杂，所以有了咱们的集合数据类型。

1.用途：

用于关系运算的集合体，因为集合内的元素无序且集合元素不可重复，所以集合能够去重，可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，每一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.经常使用操做+内置方法：

集合的相关方法

 1.长度len

 2.成员运算in和not in

 3.|并集、union

 4.&交集、intersection

 5.-差集、difference

 6.^对称差集、symmetric_difference

 7.==

 8.父集：>、>= 、issuperset

 9.子集：<、<= 、issubset

 10.add

 11.remove

 12.difference_update

 13.discard

 14.isdisjoint

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 = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}

print(f"pythoners|linuxers: {pythoners|linuxers}")
print(f"pythoners.union(linuxers): {pythoners.union(linuxers)}")

\# union:联合的意思 pythoners|linuxers: {'nash', 'langyigang', 'jinyi', 'yankeming', 'fujiancheng', 'zhaoyanrun'} pythoners.union(linuxers): {'nash', 'langyigang', 'jinyi', 'yankeming', 'fujiancheng', 'zhaoyanrun'}
4.&交集

# str之&交集
pythoners = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}

print(f"pythoners&linuxers: {pythoners&linuxers}")
print(f"pythoners.intersection(linuxers): {pythoners.intersection(linuxers)}")

\# intersection:交集 pythoners&linuxers: {'nash'} pythoners.intersection(linuxers): {'nash'}
5.-差集

# str之-差集
pythoners = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}

print(f"pythoners-linuxers: {pythoners-linuxers}")
print(f"pythoners.difference(linuxers): {pythoners.difference(linuxers)}")

\# difference:反向差集 pythoners-linuxers: {'langyigang', 'fujiancheng', 'jinyi'} pythoners.difference(linuxers): {'langyigang', 'fujiancheng', 'jinyi'}

6.^对称差集

# str之^对称差集
pythoners = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}

print(f"pythoners^linuxers: {pythoners^linuxers}")
print(
    f"pythoners.symmetric_difference(linuxers): {pythoners.symmetric_difference(linuxers)}")

\# symmetric_difference:对称差集 pythoners^linuxers: {'fujiancheng', 'yankeming', 'jinyi', 'zhaoyanrun', 'langyigang'} pythoners.symmetric_difference(linuxers): {'fujiancheng', 'yankeming', 'jinyi', 'zhaoyanrun', 'langyigang'}
7.==

# str之==
pythoners = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}
javers = {'nash', 'yankeming', 'zhaoyanrun'}

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 = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}
javaers = {'nash', 'zhanyanrun'}

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)}")

\# issuperset:子集 pythoners>linuxers: False pythoners>=linuxers: False pythoners>=javaers: False pythoners.issuperset(javaers): False
9.子集：<、<=

# str之子集：<、<=
pythoners = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}
javaers = {'nash', 'zhanyanrun'}

print(f"pythoners<linuxers: {pythoners<linuxers}")
print(f"pythoners<=linuxers: {pythoners<=linuxers}")
print(f"javaers.issubset(javaers): {javaers.issubset(javaers)}")

\# issuperset:子集 pythoners<linuxers: False pythoners<=linuxers: False javaers.issubset(javaers): True
10.add

# set之add()
s = {1, 2, 'a'}
s.add(3)

print(s)

{1, 2, 3, 'a'}

11.remove

# set之remove()
s = {1, 2, 'a'}
s.remove(1)

print(s)

{2, 'a'}

12.difference_update

# str之difference_update()
pythoners = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyanrun', 'yankeming'}
pythoners.difference_update(linuxers)

print(f"pythoners.difference_update(linuxers): {pythoners}")

pythoners.difference_update(linuxers): {'fujiancheng', 'langyigang', 'jinyi'}

13.discard

# set之discard()
s = {1, 2, 'a'}
# s.remove(3)  # 报错
s.discard(3)

print(s)

{1, 2, 'a'}

14.isdisjoint

# set之isdisjoint()，集合没有共同的部分返回True，不然返回False
pythoners = {'nash', 'langyigang', 'fujiancheng', 'jinyi'}
linuxers = {'nash', 'zhaoyantun', 'yankeming'}
pythoners.isdisjoint(linuxers)

print(f"pythoners.isdisjoint(linuxers): {pythoners.isdisjoint(linuxers)}")

pythoners.isdisjoint(linuxers): False

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:4480523848 second:4480523848

6.可变or不可变：

可变数据类型