python-字典的使用

#字典key:value
info = {'stu1101':{'yangyang':['lan','chou']},'stu1102':'liangyan','stu1103':'yangboyu','stu1104':'liangshuang'}
#字典是无序的，且key值必须是唯一的
print(info['stu1101'])#通过key值查询对应value值
info['stu1101']='杨洋'#修改key值为stu1101的value值

#del删除
del info['stu1101']#删除key为stu1101的值
info.pop('stu1102')#同上
info.popitem()#随机删一个

print(info)


info = {'stu1101':'yangyang','stu1102':'liangyan','stu1103':'yangboyu','stu1104':'liangshuang'}
# print(info['stu1105'])#查询key值为stu1105的值，若不存在则报错
print(info.get('stu1105'))#通过这种方法去取值，如果没有返回none，不会报错，上面方法会报错
print('stu1105' in info)#查询key值是否在字典里，返回True or False,
print(info.has_key('stu1101'))#与上面命令相同

print(info)



#key不要写中文
info = {'stu1101':{'yangyang':['lan','chou']},'stu1102':'liangyan','stu1103':'yangboyu','stu1104':'liangshuang'}

info['stu1101']['yangyang'][1] = 'ai'#修改值
print(info.values())#打印所有value值
print(info.keys())#打印所有key值
info.setdefault('stu1104',{'liangxing':['gao','shou']})#如果不存在，则创建，存在，则不执行
print info


b = {
    'stu1101':'alex',
    1:3,
    2:5
}
info.update(b)#吧两个字典合并，有交叉就覆盖，没有就创建

print info.items()#把字典转换成列表
c = dict.fromkeys([6,7,8],[1,2,3])#初始化一个字典，前面是key，后面是值,所有key值都对应同一个value值
print c


for i in info:
    print i,info[i]

for k,v in info.items():
        print k,v

#当列表里的值为tuple，那么循环取值时，当for后面有一个变量，就取tuple，当多余1个变量，那么变量个数就必须与tuple里值个数一至，且各tuple之间也必须存在相同个数的值
list = [(1,'one'),(2,'two'),(3,'shree')]
for i,k in list:
    print i,k

print  dict(list)#将list变为字段