字典方法

keys()　　# 返回字典所有的键

dic = {'key1':'value1', 'key2':'value2'}

print(dic.keys())    # dict_keys(['key1', 'key2'])

 value()　　# 返回字典中的所有值

dic = {'key1':'value1', 'key2':'value2'}

print(dic.values())    # dict_values(['value1', 'value2'])

items()　　# 返回可遍历的(键, 值) 元组数组

dic = {'key1':'value1', 'key2':'value2'}

print(dic.items())    # dict_items([('key1', 'value1'), ('key2', 'value2')])

get(k, d=None)　　# 根据key获取值，key不存在时，可以指定返回值（默认为：None）

dic = {'key1':'value1', 'key2':'value2'}

var = dic.get('key1')
print(var)    # value1

var = dic.get('key')
print(var)    # None

update()　　# 更新字典

dic = {'key1':'value1', 'key2':'value2'}

dic.update({'key1':'xiaoming', 'key2':'abc'})
print(dic)    # {'key1':'xiaoming', 'key2':'abc'}

dic.update(key1='eee', key2='name')
print(dic)    # {'key1':'eee', 'key2':'name'}

# 如果字典中没有key则会添加进去
dic.update(key3='aaa', key4='bbb')
print(dic)    #{'key1':'eee', 'key2':'name', 'key3':'aaa', 'key4':'bbb'}

dict.fromkeys(seq[,value])　　# 用于创建一个新字典，以序列seq中元素做字典的键，value为字典所有键对应的初始值

dic = dict.fromkeys({'key1', 'key2', 'key3'},'xiaoming')
print(dic)    # {'key1':'xiaoming', 'key2':'xiaoming', 'key3':'xiaoming'}

clear()　　# 清空字典

dic = {'key1':'value1', 'key2':'value2'}

dic.clear()
print(dic)    # {}

copy()　　# 拷贝

dic = {'key1':'value1', 'key2':'value2'}

var = dic.copy()
print(var)    # {'key1':'value1', 'key2':'value2'}

pop(k, d=None)　　# 删除key对应的值，并返回被删除的值，key不存在时，返回指定值（默认为：None）

dic = {'key1':'value1', 'key2':'value2'}

var = dic.pop('key1')
print(dic,var)    # {'key2':'value2'} value1

var = dic.pop('key3','null')
print(var)    # null

popitem()　　# 随机返回并删除字典中的一对键和值(一般删除末尾对)

dic = {'key1':'value1', 'key2':'value2'}

var = dic.popitem()
print(dic,var)    # {'key1': 'value1'} ('key2', 'value2')

setdefault(k[,d=None])　　# 设置值，已经key存在，不设置，获取当前key对应的值，key不存在，设置，获取当前可以对应的值（默认为：None）

dic = {'key1':'value1', 'key2':'value2'}

var = dic.setdefault('key1','xiaoming')
print(dic,var)    # {'key1': 'value1', 'key2': 'value2'} value1

var = dic.setdefault('key3','xiaoming')
print(dic,var)    # {'key1': 'value1', 'key2': 'value2', 'key3': 'xiaoming'} xiaoming