版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/csdnlinyongsheng/article/details/83858113
本章内容
1.集合
2.深浅Copy
一、集合
集合(set)是一个无序的不重复元素序列。可以使用大括号{}或 set()函数创建集合。
注意:创建一个空集合必须用 set()而不是{}, 因为{}是用来创建一个空集字典。
1.创建
set1 = set({1,2,'barry'})
set2 = {1,2,'barry'}
print(set1,set2) # {1, 2, 'barry'} {1, 2, 'barry'}
2.增
set1 = {'alex','wusir','ritian','egon','barry'}
set1.add('景女神')
print(set1)
#update:迭代着增加
set1.update('A')
print(set1)
set1.update('老师')
print(set1)
set1.update([1,2,3])
print(set1)
3.删
set1 = {'alex','wusir','ritian','egon','barry'}
set1.remove('alex') # 删除一个元素
print(set1)
set1.pop() # 随机删除一个元素
print(set1)
set1.clear() # 清空集合
print(set1)
del set1 # 删除集合
print(set1)
4.其它操作
4.1 交集(& 或者 intersection)
set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 & set2) # {4, 5}
print(set1.intersection(set2)) # {4, 5}
4.2 并集(| 或者 union)
set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 | set2) # {1, 2, 3, 4, 5, 6, 7, 8}
print(set2.union(set1)) # {1, 2, 3, 4, 5, 6, 7, 8}
4.3 差集(- 或者 difference)
set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 - set2) # {1, 2, 3}
print(set1.difference(set2)) # {1, 2, 3}
4.4 反交集(^ 或者 symmetric_difference)
set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 ^ set2) # {1, 2, 3, 6, 7, 8}
print(set1.symmetric_difference(set2)) # {1, 2, 3, 6, 7, 8}
4.5 子集与超集
set1 = {1,2,3}
set2 = {1,2,3,4,5,6}
print(set1 < set2)
print(set1.issubset(set2)) # 这两个相同,都是说明set1是set2子集。
print(set2 > set1)
print(set2.issuperset(set1)) # 这两个相同,都是说明set2是set1超集。
5.frozenset不可变集合,让集合变成不可变类型
s = frozenset('barry')
print(s,type(s)) # frozenset({'a', 'y', 'b', 'r'}) <class 'frozenset'>
二、深浅Copy
1.赋值运算
l1 = [1,2,3,['barry','alex']]
l2 = l1
l1[0] = 111
print(l1, id(l1)) # [111, 2, 3, ['barry', 'alex']]
print(l2, id(l2)) # [111, 2, 3, ['barry', 'alex']]
l1[3][0] = 'wusir'
print(l1, id(l1)) # [111, 2, 3, ['wusir', 'alex']]
print(l2, id(l2)) # [111, 2, 3, ['wusir', 'alex']]
总结:l1与l2指向同一个内存地址
2.深浅拷贝Copy
l1 = [1,2,3,['barry','alex']]
l2 = l1.copy()
print(l1,id(l1)) # [1, 2, 3, ['barry', 'alex']] 2380296895816
print(l2,id(l2)) # [1, 2, 3, ['barry', 'alex']] 2380296895048
l1[1] = 222
print(l1,id(l1)) # [1, 222, 3, ['barry', 'alex']] 2593038941128
print(l2,id(l2)) # [1, 2, 3, ['barry', 'alex']] 2593038941896
l1[3][0] = 'wusir'
print(l1,id(l1[3])) # [1, 2, 3, ['wusir', 'alex']] 1732315659016
print(l2,id(l2[3])) # [1, 2, 3, ['wusir', 'alex']] 1732315659016
总结:从得出的结果可以看出,第一层浅拷贝复制成功,第二层深拷贝没有成功
3.深拷贝Copy
import copy
l1 = [1,2,3,['barry','alex']]
l2 = copy.deepcopy(l1)
print(l1,id(l1)) # [1, 2, 3, ['barry', 'alex']] 2915377167816
print(l2,id(l2)) # [1, 2, 3, ['barry', 'alex']] 2915377167048
l1[1] = 222
print(l1,id(l1)) # [1, 222, 3, ['barry', 'alex']] 2915377167816
print(l2,id(l2)) # [1, 2, 3, ['barry', 'alex']] 2915377167048
l1[3][0] = 'wusir'
print(l1,id(l1[3])) # [1, 222, 3, ['wusir', 'alex']] 2915377167240
print(l2,id(l2[3])) # [1, 2, 3, ['barry', 'alex']] 2915377167304
总结:以上可看出,两个列表完全独立,改变任意一个元素,不会影响另一个元素