python基础三

Posted 2020-08-15

多级菜单

• 多级菜单
• 可依次选择进入各子菜单
• 所需新知识点：列表、字典

#!/usr/bin/env python
# -*- coding: utf-8 -*-
menu = {
    ‘北京‘:{
        ‘海淀‘:{
            ‘五道口‘:{
                ‘soho‘:{},
                ‘网易‘:{},
                ‘google‘:{}
            },
            ‘中关村‘:{
                ‘爱奇艺‘:{},
                ‘汽车之家‘:{},
                ‘youku‘:{},
            },
            ‘上地‘:{
                ‘百度‘:{},
            },
        },
        ‘昌平‘:{
            ‘沙河‘:{
                ‘老男孩‘:{},
                ‘北航‘:{},
            },
            ‘天通苑‘:{},
            ‘回龙观‘:{},
        },
        ‘朝阳‘:{},
        ‘东城‘:{},
    },
    ‘上海‘:{
        ‘闵行‘:{
            "人民广场":{
                ‘炸鸡店‘:{}
            }
        },
        ‘闸北‘:{
            ‘火车战‘:{
                ‘携程‘:{}
            }
        },
        ‘浦东‘:{},
    },
    ‘山东‘:{},
}

current_level = menu
last_level = []

while True:
    for key in current_level:
        print(key)
    choice = input(">>:").strip()
    if len(choice) ==0:break
    if choice ==‘b‘:
        if len(last_level)==0:break
        current_level = last_level[-1]
        last_level.pop()
    if choice not in current_level:continue
    last_level.append(current_level)
    current_level = current_level[choice]

 

字典

查询

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}


print(dic[‘name‘])
print(dic.get(‘namedf‘))#用get，如果没有这个值，查询不会报错

 

以上代码运行结果

alex
None

 

add

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}

dic[‘gender‘]=‘female‘
print(dic)#打印字典是无序的

 

以上代码运行结果

{‘age‘: 18, ‘gender‘: ‘female‘, ‘name‘: ‘alex‘}

 

change

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}

dic[‘name‘]=‘lhf‘
print(dic)

 

以上代码运行结果

{‘name‘: ‘lhf‘, ‘age‘: 18}

 

del

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}

del dic[‘name‘]
print(dic)

 

以上代码运行结果

{‘age‘: 18}

 

字典里嵌入其它数据类型

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic1={
    1:‘alex‘,
    ‘name‘:‘lhf‘,
    (1,2,3):{‘age‘:18},
    ‘name‘:‘alex‘
}

print(dic1[1])
print(dic1[‘name‘])
print(dic1[(1,2,3)])
print(dic1[(1,2,3)][‘age‘])

 

以上代码运行结果

alex
alex
{‘age‘: 18}
18

 

字典的其它用法

#!/usr/bin/env python
# -*- coding: utf-8 -*-

dic1=dict.fromkeys(‘abc‘,1)
print(dic1)

 

以上代码运行结果（注意：此处类似浅拷贝）

{‘b‘: 1, ‘c‘: 1, ‘a‘: 1}

 

 

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}

dic2 =dict.fromkeys([‘a‘,‘b‘],1)
print(dic2)
print(dic.get(‘name‘))

 

以上代码运行结果

{‘b‘: 1, ‘a‘: 1}
alex

 

 

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}


for k,v in dic.items():
    print(k,v)
print(dic.keys())
for i in dic.keys():
    print(‘key is %s,value is %s‘%(i,dic[i]))

 

以上代码运行结果

age 18
name alex
dict_keys([‘age‘, ‘name‘])
key is age,value is 18
key is name,value is alex

 

指定删除

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}


dic.pop(‘name‘)
print(dic)

 

以上代码运行结果

{‘age‘: 18}

 

随机删除

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}

dic.popitem()
print(dic)

 

以上代码运行结果

{‘name‘: ‘alex‘}

 

 

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}


dic.setdefault(‘gender‘,[]).append(‘male‘)
dic[‘gender‘].append(‘female‘)

 

以上代码运行结果

{‘age‘: 18, ‘name‘: ‘alex‘, ‘gender‘: [‘male‘, ‘female‘]}

 

 

__author__ = "zhou"
#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}
dic1 = {‘gender‘:‘male‘,‘name‘:‘ldf‘}

dic.update(dic1)
print(dic)

 

以上代码运行结果

{‘name‘: ‘ldf‘, ‘age‘: 18, ‘gender‘: ‘male‘}

 

常用的取字典里面键值的方法

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic={‘name‘:‘alex‘,‘age‘:18}

for k in dic:
    print(k,dic[k])
for i in dic.values():
    print(i)

 

以上代码运行结果

age 18
name alex
18
alex

 

浅拷贝

#!/usr/bin/env python
# -*- coding: utf-8 -*-
dic ={‘name‘:‘alex‘,‘age‘:18,‘gfs‘:["Monkey","Cythrina","Rachel"]}

dic2=dic.copy()
print(dic)
print(dic2)
dic2["name"]="Jack"

dic2["gfs"][2] = "hhhh"
print(dic)
print(dic2)

 

以上代码运行结果

{‘gfs‘: [‘Monkey‘, ‘Cythrina‘, ‘Rachel‘], ‘name‘: ‘alex‘, ‘age‘: 18}
{‘gfs‘: [‘Monkey‘, ‘Cythrina‘, ‘Rachel‘], ‘name‘: ‘alex‘, ‘age‘: 18}
{‘gfs‘: [‘Monkey‘, ‘Cythrina‘, ‘hhhh‘], ‘name‘: ‘alex‘, ‘age‘: 18}
{‘gfs‘: [‘Monkey‘, ‘Cythrina‘, ‘hhhh‘], ‘name‘: ‘Jack‘, ‘age‘: 18}

集合

 

 

 

 

 

 

字符编码

字符---gb2313--->硬盘
硬盘---gb2313--->字符
字符 --->unicode--->内存

1、内存固定使用unicode编码，硬盘的编码（即你可以修改的软件编码）
2、使用什么编码往硬盘存，就用什么编码去读
3、程序运行分两阶段：
　　1、从硬盘读到内存
　　2、python解释器运行已经读到内存的代码
4、针对一个test.py文件来说python与nodpad++\vim区别是多了第二步。