python之路(集合,深浅copy,基础数据补充)

一、集合:类似列表,元组的存储数据容器,不同点是不可修改,不可重复.无序排列.

1.创建集合:

(1).set1 = {'abby', 'eric'}

result:{'eric', 'abby'}

(2).set2 = set({'abby', 'eric'})

result:{'abby', 'eric'}

2.增

set1 = {'abby','eric','allan','davy','skye'}

(1).set1.add('west')

result:{'west','abby','eric','allan','davy','skye'}

(2).set1.update('abc')#迭代新增

result:{'west','abby','a','eric','allan','c','davy','b','skye'}

3.删

set1 = {'abby','eric','allan','davy','skye'}

(1).set1.remove('abby')#指定删除

result:{'eric','allan','davy','skye'}

(2).set1.pop()#随机删除

result:{'abby','eric','allan','skye'}

(3).set clear()#清空集合

result:set()

(4).del set1#从内存删除集合

result:name 'set1' is not defined

4.关系测试:

set1 = {1,2,3,4,5}

set2 = {4,5,6,7,8}

(1).交集:

1:print(set1 & set2)

2:print(set1.intersection(set2)

result:{4,5}

(2).并集

1:print(set1 | set2)

2:print(set1.union(set2)

result:{1, 2, 3, 4, 5, 6, 7, 8}

(3).反交集

1:print(set1 ^ set2)

2:print(set1.symmetric_difference(set2)

result:{1, 2, 3, 6, 7, 8}

(4).差集

1:print(set1 - set2)

2:print(set1.difference(set2)

result:{1, 2, 3}

3.print(set2-set1)

4.print(set2.difference(set1)

result:{8, 6, 7}

(5)子集

set1 = {1,2,3}

set2 = {1,2,3,4,5,6}

print(set1 < set2)

print(set1.issubset(set2))

result:True

(5)超集

print(set2 > set1)

print(set2.issuperset(set1))

result:True

(6)冻结,不可变的数据类型

set1 = {1,2,3}

set3 = frozenset(set1)

result:frozenset({1, 2, 3})

面试题:list去重

l1 = [1,1,2,3,4,4,3,2,1,5,5]

set1 = set(l1)

l2 = list(set1)

print(l2)

二、深浅copy

1. 赋值运算

l1 = [1,2,3]

l2 = l1

l1.append(666)

print(l2)

print(id(l1))

print(id(l2))

result:

[1, 2, 3, 666]

2724735509128

2724735509128

2.浅copy

test01:

l1 = [1,2,3]

l2 = l1.copy()

l1.append(666)

print(l2)

result:[1, 2, 3]

test02:

l1 = [1,2,3,[22,]]

l2 = l1.copy()

l1.append(666)

print(l1,l2)

result:[1, 2, 3, [22], 666] [1, 2, 3, [22]]

test03:

l1 = [1,2,3,[22,]]

l2 = l1.copy()

l1[-1].append('abby')

print(l1,l2)

print(id(l1))

print(id(l2))

print(id(l1[-1]))

print(id(l2[-1]))

result:

[1, 2, 3, [22, 'abby']] [1, 2, 3, [22, 'abby']]
2586054582984
2586055807688
2586054582920
2586054582920

3.深copy

需要copy模块

import copy

l1 = [1,2,3,[22,]]

l2 = copy.deepcopy(l1)

l1.append(666)

print(l2)

result:[1, 2, 3, [22]]

总结深浅copy:都是copy,浅copy复制第一层独立存在,第二层与复制对象共同拥有.深copy复制所有层并且独立存在

面试题:

l1 = [1,2,3,[22,33]]

l2 = l1[:]

l1.append(666)

print(l2)

result:[1, 2, 3, [22, 33]]

总结:切片属于浅copy

三、基础数据补充

1.数据类型的转换

# str ---> list

s1 = 'abby eric west'

l1 = s1.split()

print(l1)

result:['abby', 'eric', 'west']

l1 = ['abby', 'eric', 'west']

s2 = ' '.join(l1)

print(s2)

result:abby eric west

# tuple <---> list

l1 = [1,2,3]

tu1 = tuple(l1)

print(tu1)

result:(1, 2, 3)

tu2 = (0,2,3)

l1 = list(tu2)

print(l1)

result:[0, 2, 3]

# dic ---> list

dic1 = {'name': 'alex', 'age': 1000}

l1 = list(dic1)

print(l1)

result:['name', 'age']

bool转换

0 " [] () {} set() ---> bool: False

四、enumerate枚举

字典用法:

dic01 = {'key1': 'value1','key2': 'value2', 'k3':'v3', 'name': 'abby'}

1.for i in enumerate(dic01,1):#1为索引起始位

　　print(i)

result:

(1, 'key1')
(2, 'key2')
(3, 'k3')
(4, 'name')

2.for a,b in enumerate(dic01,1):

　　print(a,b)

result:

1 key1
2 key2
3 k3
4 name

列表:li01 = [1,2,3,4,5,6,7,8]

for i in enumerate(li01,1):

　　print(i)

result:

(1, 1)
(2, 2)
(3, 3)
(4, 4)
(5, 5)
(6, 6)
(7, 7)
(8, 8)

for a,b in enumerate(li01,1):

　　print(a,b)

result:

1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8