python 有序字典

import collections
dic=collections.OrderedDict()
# dic['k1']='v1'
# dic['k2']='v2'
# dic['k3']='v3'
a=('k1','k2','k3')
dic1=dic.fromkeys(a,1)
print(dic)
print(dic1)
控制台打印：OrderedDict([('k1', 1), ('k2', 1), ('k3', 1)])

dic=collections.OrderedDict()
dic['k1']='v1'
dic['k2']='v2'
dic['k3']='v3'
OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')])
打印出来的都是有顺序的

dic.move_to_end('k1')#把k1放在最后面
print(dic)
OrderedDict([('k2', 'v2'), ('k3', 'v3'), ('k1', 'v1')])

a=dic.pop('k1')#删除指定的item
print(a)
print(dic)

v1
OrderedDict([('k2', 'v2'), ('k3', 'v3')])

dic1=dic.popitem()#删除最后一个，并返回
print(dic)
print(dic1)

OrderedDict([('k1', 'v1'), ('k2', 'v2')])
('k3', 'v3')

dic.setdefault('k4',2)
print(dic)
OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3'), ('k4', 2)])