标签：user 个数 应该 集合 word 区别 pre 成员 python3
一.字典 dict
1.记录多个值,key是用来描述value的特征
2.定义
在{}内有多个key:value值,用逗号分开, # value可以是任意数据类型,key必须是不可变类型,通常情况下为字符串 # a = {‘name‘:‘jason‘,‘password‘:123} # a = dict({‘name‘:‘jason‘,‘password‘:123}) # print(a,type(a)) # print(a[‘name‘]) # print(a[‘password‘])
3.用法
# 用法一 # a = dict(x =1,y = 2,z = 3) # print(a) # {‘x‘: 1, ‘y‘: 2, ‘z‘: 3} # 用法二 # userinfo = [ # [‘name‘,‘jason‘], # [‘age‘,18], # [‘sex‘,‘male‘] # ] # d = {} # for k,v in userinfo: # d[k]=v # print(d) # {‘name‘: ‘jason‘, ‘age‘: 18, ‘sex‘: ‘male‘}
4.常用操作和内置方法
1.按key取值,可取可换,则有序的
# a = {‘name‘:‘jason‘,‘password‘:223} # print(a[‘name‘]) # print(a[‘password‘]) # a[‘name‘] = ‘egon‘ # print(a) # a[‘password‘] = 123 # print(a)
2.长度len():统计的是key:value的个数
# a = {‘name‘:‘jason‘,‘password‘:123} # # print(a) # # print(len(a))
3.成员运算in和not in
字典中成员运算判读的是key
# a = {‘name‘:‘jason‘,‘password‘:123} # print(‘name‘ in a) # True # print(123 in a) # False
4.删除
# a = {‘name‘:‘jason‘,‘password‘:123} # 通用的del:删除整个key:value键值对 # del a[‘name‘] # print(a) # del a[‘age‘] # print(a) # 不存在报错 # pop 删除的key对应的值,返回value值.应该叫弹出 # a = {‘name‘:‘jason‘,‘password‘:123} # res = a.pop(‘name‘) # print(res) # jason # print(a) # popitem 删除的是后面的key:value.应该叫弹出 # a = {‘name‘:‘jason‘,‘password‘:123} # res = a.popitem() # print(res) # print(a)
5.键keys(),值values(),键值对iiems()
注意:在Python2 和Python3的区别
在Python2中是列表,在Python3中是元组
# dic = {‘name‘:‘egon‘,‘age‘:18} # print(dic.keys()) # print(dic.values()) # print(dic.items()) # dict_keys([‘name‘, ‘age‘]) # dict_values([‘egon‘, 18]) # dict_items([(‘name‘, ‘egon‘), (‘age‘, 18)])
6.循环
# dic = {‘name‘:‘egon‘,‘age‘:18,‘sex‘:‘male‘} # for k in dic.keys(): # print(k,dic[k]) # name egon # age 18 # sex male
7.get() 和按key取值比较就是不报错
# dic = {‘name‘:‘egon‘,‘age‘:123,‘sex‘:‘male‘} # # dic[‘aaa‘] # 报错 # # v = dic.get(‘name‘) # # print(v) # # # # v = dic.get(‘sss‘) # # print(v) # None 不报错
8.总结:
存多个值
无序的
可变
二.元组 tuple
与列表相比也可存多个值,但元组内的元素不能够改变
1,用途:存多个值,值没有被改的需要
2.定义:
()内的元素是任意数据类型,元组之间用逗号隔开
# a = (2,2.2,‘jason‘,[1,2]) # a = tuple(2,2.2,‘jason‘,[1,2]) # print(a,type(a)) # a1 = tuple(‘hello‘) # print(a1) # (‘h‘, ‘e‘, ‘l‘, ‘l‘, ‘o‘) # 元组内部for循环,得到是元组
3.常用操作
1,索引取值,不能够改. 有序的
# a = (1,1.1,‘jason‘,[1,2]) # print(id(a)) # 2777382289640 # print(id(a[0])) # print(id(a[1])) # print(id(a[2])) # print(id(a[3])) # a[3][0] = 3 # 整形替换整形 # print(id(a)) # 2777382289640
2,切片(顾头不顾尾)
# a = (1,2,3,4) # print(a[0:2]) # (1, 2) # print(a) # (1, 2, 3, 4)
3,长度len()
# a = (1,2,3,4) # a1 = len(a) # print(a1) # 4
4.成员运算in和not in
a = (1,2,3) print(1 in a)
5.循环
# a = (1,2,3,4) # for i in a: # print(i)
4.内置方法
1,count 统计count括号内元素在元组中的个数
# a = (1,2,3,4) # res = a.count(1) # print(res) # print(a)
2.index() 查找index括号内的元素在元组中的索引位置,可加范围查找
t=(‘a‘,‘b‘,‘c‘,‘a‘) print(t.index(‘a‘,1,4)) # print(t.index(‘xxx‘,1,10)) # 报错
三.集合 set
# pythons = [‘李二丫‘,‘张金丹‘,‘李银丹‘,‘赵同丹‘,‘张铁蛋‘,‘alex‘,‘oldboy‘] # linux = [‘lxx‘,‘egon‘,‘张金丹‘,‘张译丹‘,‘alex‘,‘陈独秀‘] # l = [] # for students in pythons: # if students in linux: # l.append(students) # print(l)
1.用途:运算关系 去重
2.定义方式:在{}内用逗号分隔各个元素
3.集合的三大特性
(1),每个值都是不可变的
(2),元素不能重复
(3),集合内的元素是无序的
# a = {1,1.1,‘Jason‘,(1,2)} # a = ser{1,1.1,‘Jason‘,(1,2) # print(a,type(a)) # {‘Jason‘, 1, (1, 2), 1.1} <class ‘set‘> # a = {1,1,22,22,3,6,6} # print(a) # {1, 3, 22, 6} # a = {1,‘a‘,2,‘s‘} # a[0] # 报错
4.常用操作和内置方法
# a = {1,2,3,4,5} # b = {3,4,5,6,7} # # 提取a,b中相同的数字.集合 # print(a & b) # {3, 4, 5} # print(a.intersection(b)) # # # 提取a和b的并集 # print(a | b) # {1, 2, 3, 4, 5, 6, 7} # print(a.union(b)) # # # a 和 b的差集 # print(a - b) # 1, 2} # print(a.difference(b)) # print(b - a) # {6, 7} # print(b.difference(a)) # # # a和b都有 交集 # print(a ^ b) # {1, 2, 6, 7} # print(a.symmetric_difference((b))) # 是否相等 # a = {1,2,3,4,5} # b = {1,2,3,5,4} # print(a == b) # True # 无序的 # 子集 # a = {1,2,3,4} # b = {1,2,3,5,4} # print(b >= a)
内置方法
# 1.update # a = {1,2,3,4} # a.update({3,4,5}) # print(a) # 2.add # a = {1,2,3,4} # a.add(5) # print(a) # 3.pop # a ={1,2,3,4} # res = a.pop() # print(a) # print(res) # 4.remove # a = {1,2,3,4} # res = a.remove(3) # print(a) # print(res) # None # 删除的元素不存在不报错 # 5.difference_update() 和difference相同 # a = {1,2,3,4} # a1 = {1,2} # a.difference_update(a1) # print(a) # a.difference(a1) # print(a) # {3, 4} # 6.discard() # a = {1,2,3,4} # res = a.discard(3) # # print(res) # None # print(a) # {1, 2, 4} # 删除的元素不存在不报错 # 7.isdisjoint() # a = {1,2,3} # a1 = {1,2,4} # print(a.isdisjoint(a1)) # 两个集合没有交集这为真
5.集合去重
局限性
1,无法保证原数据的顺序
2,当一个数据包含多个值,每个值为不可变类型才能用集合去重
# names ={‘alex‘,‘egon‘,‘alex‘,‘alex‘,‘egon‘,‘lxx‘} # s = set(names) # print(s) # a = list(s) # print(a) # students = [ # {‘name‘:‘egon‘,‘age‘:18}, # {‘name‘:‘jason‘,‘age‘:19}, # {‘name‘:‘oldboy‘,‘age‘:20}, # {‘name‘:‘egon‘,‘age‘:18}, # {‘name‘:‘jason‘,‘age‘:19}, # ] # # set(students) # 报错 # # a = [] # for info in students: # if info not in a: # a.append(info) # # print(a) # students = a # print(students)
总结
1,存多个值
2,无序
3,可变类型
标签：user 个数 应该 集合 word 区别 pre 成员 python3
原文地址：https://www.cnblogs.com/zhuangshenhao/p/11134891.html
