python入门：字符串2

字符串2

元组类型：tuple

当多个值只有读的需求，没有改的需求是，使用元组更合适

定义方式：在（）使用，分割开的任意值（元组是不可变类型）

msg=(1,2,'a',['b','c'])
print(type(msg))
print(msg)
print(msg[3][1])
t=tuple('hello') #直接定义一个元组
print(t[2])

#结果

(1, 2, 'a', ['b', 'c'])
c
l

元组里面包含的列表是可以修改的

msg=(1,2,'a',['b','c'])
t=msg[3][0]='x'
print(msg)

#结果
(1, 2, 'a', ['x', 'c'])

元组内置方法：

count

msg=(1,'2','a',['b','c']) #统计不到列表里面的
print(msg.count('a'))#统计
#结果
1

index

msg=(1,'2','a',['b','c']) #查询不到列表里面的
print(msg.index('a'))
print(msg.index(['b','c']))
#结果
2
3

字典：

字典类型：class

定义方式：在{}内用逗号分隔开多 个key:value，其中value可以是任意类型，而key必须是不可变的类型，通常情况下应该str类型

# dic={0:'aaa',1:'bbb',2:'cccc'} #dic=dict({0:'aaa',1:'bbb',2:'cccc'})
# print(dic,type(dic))
# print(dic[0])

# dic={[1,2]:'aaa'}
# dic={(1,2):'aaa'}
# print(dic[(1,2)])

# 用法一：
# dic=dict(x=1,y=2,z=3)
# print(dic)

# 用法二：
# userinfo=[
#     ['name','egon'],
#     ['age',18],
#     ['sex','male']
# ]
# d={}
# for k,v in userinfo: #k,v=['name', 'egon']
#     # print(k,v)
#     d[k]=v
# print(d)

# d=dict(userinfo)
# print(d)

# 3 常用操作+内置的方法
#优先掌握的操作：
#1、按key存取值：可存可取
# dic={'name':'egon'}
# print(dic['name'])
# dic['name']='EGON'
# print(dic)
# dic['age']=18
# print(dic)

# l=['a','b']
# l[0]='A'
# l[2]='c'

#2、长度len
# dic={'name':'egon','age':18,'name':'EGON','name':'XXXX'}
# print(dic)
# print(len(dic))

#3、成员运算in和not in:字典的成员运算判断的是key
# dic={'name':'egon','age':18,}
# print(18 in dic)
# print('age' in dic)

#4、删除
dic={'name':'egon','age':18,}
# 通用
# del dic['name']
# print(dic)
# del dic['xxx'] ##key不存在则报错


# res=dic.pop('age') #删除key对应的value,并返回value
# print(dic)
# print(res) #
# dic.pop('xxx') #key不存在则报错

# res=dic.popitem()
# print(dic)
# print(res)

#5、键keys()，值values()，键值对items()
dic={'name':'egon','age':18,}
# print(dic.keys())
# l=[]
# for k in dic.keys():
#     l.append(k)
# print(l)
# print(list(dic.keys()))

# print(dic.values())
# print(list(dic.values()))
# print(dic.items())
# print(list(dic.items()))



#6、循环
dic={'name':'egon','age':18,'sex':'male'}

# for k in dic.keys():
#     print(k,dic[k])

# for k in dic:
#     print(k,dic[k])

# for v in dic.values():
#     print(v)

# for k,v in dic.items():
#     print(k,v)

#8 dic.get()
dic={'name':'egon','age':18,'sex':'male'}
# dic['xxx']
# v=dic.get('name')
# print(v)

# v=dic.get('xxx')
# print(v)

# 需要掌握的操作

# dic.fromkeys()的用法:
# l=['name','age','sex']
# dic={'name':None,'age':None,'sex':None}
# dic={}
# for k in l:
#     dic[k]=None
# print(dic)

# dic=dic.fromkeys(l,None)
# print(dic)


# old_dic={'name':'egon','age':18,'sex':'male'}
# new_dic={'name':'EGON','x':1,'y':2}
# old_dic.update(new_dic)
# print(old_dic)

# setdefault:有则不动/返回原值,无则添加/返回新值
# dic={'name':'egon','age':18}
# res=dic.setdefault('name','EGON') # 字典中已经存在key则不修改,返回已经存在的key对应的value
# print(dic)
# print(res)

# res=dic.setdefault('sex','male') # 字典不存在key则添加"sex":"male",返回新的value
# print(dic)
# print(res)


# #二：该类型总结
# 1 存多个值

# 2 无序
#
# 3 可变
# dic={'x':1}
# print(id(dic))
# dic['x']=2
# print(id(dic))


# 练习1:
# nums=[11,22,33,44,55,66,77,88,99,90]
# dic={
#     'k1':[],
#     'k2':[]
# }
# for num in nums:
#     if num > 66:
#         dic['k1'].append(num)
#     else:
#         dic['k2'].append(num)
# print(dic)
#

# 练习2:
# s='hello alex alex say hello sb sb'
# words=s.split()
# dic={}
# # print(words)
# for word in words:
#     if word in dic:
#         dic[word]+=1
#     else:
#         dic[word]=1
#
# print(dic)

# s='hello alex alex say hello sb sb'
# words=s.split()
# dic={}
# for word in words: # word="hello"
#     dic.setdefault(word,words.count(word)) #{'hello':2,"alex":2,"say":1,}
# print(dic)