(1)for循环
注:info.keys生成 key,info.values生成 value,info.items生成键值对。
info = {
"k1": 18,
"k2": True,
"k3": [
11,
[],
(),
22,
33,
{
'kk1': 'vv1',
'kk2': 'vv2',
'kk3': (11,22),
}
],
"k4": (11,22,33,44)
}
for item1 in info.keys():
print(item1)
print('\n')
for item2 in info.values():
print(item2)
print('\n')
for item3 in info.items():
print(item3)
返回值:
k2
k1
k4
k3
True
18
(11, 22, 33, 44)
[11, [], (), 22, 33, {'kk3': (11, 22), 'kk1': 'vv1', 'kk2': 'vv2'}]
('k2', True)
('k1', 18)
('k4', (11, 22, 33, 44))
('k3', [11, [], (), 22, 33, {'kk3': (11, 22), 'kk1': 'vv1', 'kk2': 'vv2'}])
(2)fromkeys方法(根据序列创建字典,并指定统一的 value)
v = dict.fromkeys(['th',123],999)
print(v)
返回值:{123: 999, 'th': 999}
(3)get方法(根据 key获取值,若 key不存在,获取到指定的值,默认为 None)
info = {
"k1": 18,
"k2": True,
"k3": [
11,
[],
(),
22,
33,
{
'kk1': 'vv1',
'kk2': 'vv2',
'kk3': (11, 22),
}
],
"k4": (11, 22, 33, 44)
}
v1 = info.get('k33333', 3)
v2 = info.get('k3', 333333)
print(v1, '\n', v2)
返回值:
3
[11, [], (), 22, 33, {'kk3': (11, 22), 'kk1': 'vv1', 'kk2': 'vv2'}]
(4)pop和popitem方法(删除并获取值)
注:popitem随机删除一个键值对。
dic = {
'k1': 13,
'k2': 45,
'j3': 66
}
v1 = dic.pop('k1')
print(dic, v1)
k2, v2 = dic.popitem()
print(dic, k2, v2)
返回值:
{'k2': 45, 'j3': 66} 13
{'j3': 66} k2 45
(5)setdefault方法(设置值)
注:若 key已存在,则不设置 value,获取原来的 value;若 key不存在,则添加新设置的键值对,获取新的 value。
dic1 = {
'k1': 13,
'k2': 45,
'k3': 66
}
dic2 = {
'k1': 13,
'k2': 45,
'k3': 66
}
v1 = dic1.setdefault('k1', 123)
v2 = dic2.setdefault('j3', 33)
print(dic1, v1)
print(dic2, v2)
返回值:
{'k2': 45, 'k1': 13, 'k3': 66} 13
{'j3': 33, 'k2': 45, 'k1': 13, 'k3': 66} 33
(6)update方法(更新值)
注:原字典没有的值将添加进去。
dic1 = {
'k1': 13,
'k2': 45,
'k3': 66
}
dic2 = {
'k1': 33,
'k2': 45,
'k3': 66
}
dic1.update({'k1':33,'k2':'88'})
dic2.update(k1 = 44, k2 = 55, k4 =99)
print(dic1,'\n',dic2, sep='')
返回值:
{'k1': 33, 'k3': 66, 'k2': '88'}
{'k4': 99, 'k1': 44, 'k3': 66, 'k2': 55}