一 集合 set
set集合，是一个无序且不重复的元素集合
class set(object): """ set() -> new empty set object set(iterable) -> new set object Build an unordered collection of unique elements. """ def add(self, *args, **kwargs): # real signature unknown """ Add an element to a set，添加元素 This has no effect if the element is already present. """ pass def clear(self, *args, **kwargs): # real signature unknown """ Remove all elements from this set. 清楚内容""" pass def copy(self, *args, **kwargs): # real signature unknown """ Return a shallow copy of a set. 浅拷贝 """ pass def difference(self, *args, **kwargs): # real signature unknown """ Return the difference of two or more sets as a new set. A中存在，B中不存在 (i.e. all elements that are in this set but not the others.) """ pass def difference_update(self, *args, **kwargs): # real signature unknown """ Remove all elements of another set from this set. 从当前集合中删除和B中相同的元素""" pass def discard(self, *args, **kwargs): # real signature unknown """ Remove an element from a set if it is a member. If the element is not a member, do nothing. 移除指定元素，不存在不保错 """ pass def intersection(self, *args, **kwargs): # real signature unknown """ Return the intersection of two sets as a new set. 交集 (i.e. all elements that are in both sets.) """ pass def intersection_update(self, *args, **kwargs): # real signature unknown """ Update a set with the intersection of itself and another. 取交集并更更新到A中 """ pass def isdisjoint(self, *args, **kwargs): # real signature unknown """ Return True if two sets have a null intersection. 如果没有交集，返回True，否则返回False""" pass def issubset(self, *args, **kwargs): # real signature unknown """ Report whether another set contains this set. 是否是子序列""" pass def issuperset(self, *args, **kwargs): # real signature unknown """ Report whether this set contains another set. 是否是父序列""" pass def pop(self, *args, **kwargs): # real signature unknown """ Remove and return an arbitrary set element. Raises KeyError if the set is empty. 移除元素 """ pass def remove(self, *args, **kwargs): # real signature unknown """ Remove an element from a set; it must be a member. If the element is not a member, raise a KeyError. 移除指定元素，不存在保错 """ pass def symmetric_difference(self, *args, **kwargs): # real signature unknown """ Return the symmetric difference of two sets as a new set. 对称交集 (i.e. all elements that are in exactly one of the sets.) """ pass def symmetric_difference_update(self, *args, **kwargs): # real signature unknown """ Update a set with the symmetric difference of itself and another. 对称交集，并更新到a中 """ pass def union(self, *args, **kwargs): # real signature unknown """ Return the union of sets as a new set. 并集 (i.e. all elements that are in either set.) """ pass def update(self, *args, **kwargs): # real signature unknown """ Update a set with the union of itself and others. 更新 """ pass set 集合class
#!/usr/bin/env python # _*_ coding:utf-8 _*_ __author__ = 'liujianzuo' a={1:2,4:5} b=set(a) b.add(111111) b.clear() print(b) n = {11,22,33} b = {22,66} c = {11} # n中有的b中没有的赋值给新的变量 打印 new_n = n.difference(b) print(new_n) #n中有的 b中没有的 更新到n # n.difference_update(b) # print(n) # 将迭代的序列加入 n.update("al") n.update([1,3,4]) print(n) #n存在的b不存在的 b存在n不存在的 组合一起输出 ret=n.symmetric_difference(b) ret2 = n.symmetric_difference({11,22,33}) print(ret) print("=========") # n存在的b不存在的 b存在n不存在的 组合一起 更新到前面的集合 n.symmetric_difference_update(b) print(n) # 是否是子集 不是返回false 是的话True ret = n.issubset(c) # n是不是c的子 print(ret) ret1 = c.issubset(n) # c是不是n的子 print(ret1) ret2 = n.issuperset(c) # n是不是c的父 print(ret2) # pop discard remove 三个删除的区别 #pop 删除同时可以获取到该值 ret = n.pop() #由于集合是无序的，所以pop删除也是无序的 print(ret) # discard 删除集合元素，如果元素不存在 返回False 不报错 n.discard(11) print(n) #remove 删除集合元素 如果元素不存在 报错 #n.remove(99) z = {11,22,33} p = {44} z.intersection(p) #取交集并更新到z中 print(z) 集合 练习 #!/usr/bin/env python # _*_ coding:utf-8 _*_ __author__ = 'liujianzuo' old_dict = { "#1":11, "#2":11, "#3":11, } new_dict = { "#1":33, "#4":22, "#7":100, } # b = set(old_dict.keys()) # print(b) s1 =set() s2 =set() for i in old_dict.keys(): s1.add(i) for n in new_dict: s2.add(n) print(s1,s2) ret1 = s1.difference(s2) print("for deling ：",ret1) ret2 = s2.difference(s1) print("for adding:",ret2) # ret=s1.intersection(s2) # print(ret) for i in s1 : del old_dict[i] for i in s2: old_dict[i]=new_dict[i] print(old_dict) set集合练习
交集 >>> a.append(10) >>> set(a) set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) >>> b =range(6) >>> a = set(a) >>> b =set(b) >>> a set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) >>> b set([0, 1, 2, 3, 4, 5]) 取交集 >>> a & b set([0, 1, 2, 3, 4, 5]) 交集应用场景：比如两个班级都叫alex或者两个班级都是100分的 或者两个班级中都大于多少分的 并集应用 >>> a | b set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) 差集 >>> a - b set([8, 9, 10, 6, 7]) 对称差集 >>> a - b set([8, 9, 10, 6, 7]) 把两个里面对方都没有的打印出来 A b 差集 a ^ b set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]) >>> b set([0, 1, 2, 3, 4, 5, 12]) >>> a ^ b set([6, 7, 8, 9, 10, 11, 12]) a.add集合中添加一项，同样的去重不同样的增加 >>> a.add(0) >>> a.add(22) >>> a set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 22]) a.update集合添加多项 >>> a.update([23,34,35]) >>> a set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 34, 35, 22, 23]) 添加一个集合到另一个集合 >>> a.update(b) >>> a set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 34, 35, 22, 23]) #b.issubset(a) a.issuperset(b) 测试b中的每一个元素都在a中 >>> len(a) >>> len(b) >>> b in a False >>> a in a False >>> import tab >>> b.issubset(a) #测试b中的每一个元素都在a中 True >>> a.issubset(b) False >>> 3 in a True >>> b.issuperset(a) False >>> a.issuperset(b) #测试b中的每个元素都在a中 True set集合练习
三、三元运算符
python 的三元运算
变量名 = 变量1 if 条件判断成立 else 变量2
意指: 条件成立 变量名值为变量1 否则为变量2
name = "eric" if 1 == 1 else "alex"
print("==",name)
lambda 带if条件的三元运算
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l1 = [11,22,33,44,55]# for i in l1:# if i % 2 == 0:# m = map(lambda x:x+100,[i,])# l1[l1.index(i)] = list(m)[0]# print(l1)k=map(lambda x:(x+100) if (x%2==0) else x,l1)print(list(k)) |
四 深浅拷贝
1 数字和字符串
对于 数字 和 字符串 而言，赋值、浅拷贝和深拷贝无意义，因为其永远指向同一个内存地址。
import copy # ######### 数字、字符串 ######### n1 = 123 # n1 = "i am alex age 10" print(id(n1)) # ## 赋值 ## n2 = n1 print(id(n2)) # ## 浅拷贝 ## n2 = copy.copy(n1) print(id(n2)) # ## 深拷贝 ## n3 = copy.deepcopy(n1) print(id(n3))
二、其他基本数据类型
对于字典、元祖、列表 而言，进行赋值、浅拷贝和深拷贝时，其内存地址的变化是不同的。
1、赋值
赋值，只是创建一个变量，该变量指向原来内存地址，如：
n1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}
n2 = n1
2、浅拷贝
浅拷贝，在内存中只额外创建第一层数据
import copy
n1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}
n3 = copy.copy(n1)
3、深拷贝
深拷贝，在内存中将所有的数据重新创建一份（排除最后一层，即：python内部对字符串和数字的优化） 最底层数据要满足第一条赋值变量的条件
import copy
n1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}
n4 = copy.deepcopy(n1)
