python基礎-20集合類型內置方法

集合類型內置方法(set)

集合能夠理解成一個集合體，學習Python的學生能夠是一個集合體；學習Linux的學生能夠是一個集合體。

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

# 即報名pythoners又報名linux的學生
py_li_list = []
for stu in pythoners:
    if stu in linuxers:
        py_li_list.append(stu)
print(f"pythoners and linuxers: {py_li_list}")

上述的列表方式求兩個集合體的關係運算很是複雜，所以有了咱們的集合數據類型。

1.用途：

用於關係運算的集合體，因爲集合內的元素無序且集合元素不可重複，所以集合能夠去重，可是去重後的集合會打亂原來元素的順序。

2.定義：

{}內用逗號分隔開多個元素，每一個元素必須是不可變類型。

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.經常使用操做+內置方法：

集合的相關方法

 1.長度len

 2.成員運算in和not in

 3.|並集、union

 4.&交集、intersection

 5.-差集、difference

 6.^對稱差集、symmetric_difference

 7.==

 8.父集：>、>= 、issuperset

 9.子集：<、<= 、issubset

 10.add

 11.remove

 12.difference_update

 13.discard

 14.isdisjoint

1.長度len

# set之長度len
s = {1, 2, 'a'}

print(f"len(s): {len(s)}")

len(s): 3
2.成員運算in和not in

# set之成員運算in和not in
s = {1, 2, 'a'}

print(f"1 in s: {1 in s}")

1 in s: True
3.|並集

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

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

\# union:聯合的意思 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.^對稱差集

# str之^對稱差集
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:對稱差集 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)  # 報錯
s.discard(3)

print(s)

{1, 2, 'a'}

14.isdisjoint

# set之isdisjoint()，集合沒有共同的部分返回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.存一個值or多個值：

多個值，且值爲不可變類型。

5.有序or無序：

無序

s = {1, 2, 'a'}
print(f'first:{id(s)}')
s.add(3)
print(f'second:{id(s)}')

first:4480523848 second:4480523848

6.可變or不可變：

可變數據類型