Python的字典是一种Key-value的数据类型，和js的数据格式一样。
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
54:‘asd‘,
‘address‘:‘hebei‘
} print(name)#{‘name‘: ‘zhangshan‘, 54: ‘asd‘, ‘address‘: ‘hebei‘, ‘age‘: 23
1、打印的结果和我定义字典的顺序不一样，说明字典是无序的。
2、定义了两个‘address‘ 最后定义的把之前的覆盖了 说明字典的key是唯一的。
dic[key] = value
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
54:‘asd‘,
‘address‘:‘hebei‘
}
name[‘phone‘]=‘789456‘
print(name)#{‘phone‘: ‘789456‘, ‘age‘: 23, ‘name‘: ‘zhangshan‘, ‘address‘: ‘hebei‘, 54: ‘asd‘}
pop(key) 删除指定的key
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
name.pop(‘age‘)
print(name)#{‘name‘: ‘zhangshan‘, ‘address‘: ‘beijing‘}
dic[key] = new_value
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
name[‘name‘] = ‘lisi‘
print(name)#{‘age‘: 23, ‘name‘: ‘lisi‘, ‘address‘: ‘beijing‘}
字典的查找
1 dic[key]
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
print(name[‘name‘])#zhangshan
这种方法不是很好，如果查一个不存在的key会报错。
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
print(name[‘idcode‘])
2 get(key) 如果有了就返回 没有了就是none
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
print(name.get(‘idcode‘))#None
3 in 判断这个key是不是在字典中 结果是布尔值
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
print(‘idcode‘ in name)#False
print(‘address‘ in name)#True
values() 打印所有的value
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
print(name.values())#dict_values([23, ‘zhangshan‘, ‘beijing‘])
keys() 打印所有的key
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
print(name.keys())#dict_keys([‘age‘, ‘address‘, ‘name‘])
setdefault(key,value) 先查字典，如果能查到有这个key就返回，没有就创建一个新的key,赋值value。
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
name.setdefault(‘phone‘,‘789456‘)
name.setdefault(‘age‘,25)
print(name)#{‘phone‘: ‘789456‘, ‘age‘: 23, ‘name‘: ‘zhangshan‘, ‘address‘: ‘beijing‘}
update（dic） 两个字典合并，相同的元素覆盖。
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
name2 = {
‘name‘:‘lisi‘,
‘phone‘:‘456456‘,
‘car‘:‘SKODA‘
}
name.update(name2)
print(name)#{‘age‘: 23, ‘phone‘: ‘456456‘, ‘name‘: ‘lisi‘, ‘car‘: ‘SKODA‘, ‘address‘: ‘beijing‘}
items() 字典转列表，每一组key-value 转成元组，key作为元组的第一个值，value作为元组的第二个值。
name2 = {
‘name‘:‘lisi‘,
‘phone‘:‘456456‘,
‘car‘:‘SKODA‘
}
print(name2.items())#dict_items([(‘phone‘, ‘456456‘), (‘car‘, ‘SKODA‘), (‘name‘, ‘lisi‘)])
如果是字典嵌套
name2 = {
‘name‘:‘lisi‘,
‘phone‘:‘456456‘,
‘car‘:‘SKODA‘,
‘child‘:{
‘key_1‘:1
}
}
print(name2.items())#dict_items([(‘car‘, ‘SKODA‘), (‘child‘, {‘key_1‘: 1}), (‘name‘, ‘lisi‘), (‘phone‘, ‘456456‘)])
可以看到， 嵌套的字典并没有转成元组。
1、简单的for循环
name = {
‘name‘:‘zhangshan‘,
‘age‘:23,
‘address‘:‘beijing‘,
}
for i in name:
print(i,name[i])
#####################
name zhangshan
age 23
address beijing
2、items() 转列表循环
for key,value in name.items():
print(key,value )
#######################
address beijing
name zhangshan
age 23
如果数据量很大的话，转列表的操作会很低效。
原文：http://www.cnblogs.com/qing-chen/p/7196042.html