OrderedDict類包含在collections模塊中。
from collections import OrderedDict
基本方法
創(chuàng)建有序字典
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic)
"""
輸出：OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')])
"""
clear: 清空有序字典
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic.clear()
print(dic)
"""
輸出：OrderedDict()
"""
copy: 復制有序字典
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
new_dic = dic.copy()
print(new_dic)
"""
輸出：OrderedDict([('k1', 'v1'), ('k2', 'v2')])
"""
fromkeys: 列表轉(zhuǎn)換
dic = OrderedDict()
name = ['tom','lucy','sam']
print(dic.fromkeys(name))
print(dic.fromkeys(name,20))
"""
輸出：
OrderedDict([('tom', None), ('lucy', None), ('sam', None)])
OrderedDict([('tom', 20), ('lucy', 20), ('sam', 20)])
"""
items: 返回“鍵值對”列表
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
print(dic.items())
"""
輸出：odict_items([('k1', 'v1'), ('k2', 'v2')])
"""
keys: 獲取所有key
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
print(dic.keys())
"""
輸出：odict_keys(['k1', 'k2'])
"""
move_to_end: 指定一個key，把對應的key-value移到最后
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
dic.move_to_end('k1')
print(dic)
"""
輸出：OrderedDict([('k2', 'v2'), ('k3', 'v3'), ('k1', 'v1')])
"""
pop: 獲取指定key的value，并在字典中刪除
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
k = dic.pop('k2')
print(k,dic)
"""
輸出：v2 OrderedDict([('k1', 'v1'), ('k3', 'v3')])
"""
popitem: 按照后進先出原則，刪除最后加入的元素，返回key-value
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic.popitem(),dic)
print(dic.popitem(),dic)
"""
輸出
('k3', 'v3') OrderedDict([('k1', 'v1'), ('k2', 'v2')])
('k2', 'v2') OrderedDict([('k1', 'v1')])
"""
setdefault: 獲取指定key的value，如果key不存在，則創(chuàng)建
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
val = dic.setdefault('k5')
print(val,dic)
"""
輸出：None OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3'), ('k5', None)])
"""
values: 獲取字典所有的value，返回一個列表
dic = OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic.values())
"""
輸出：odict_values(['v1', 'v2', 'v3'])
"""
注意
普通字典不考慮存儲順序，有序字典的順序與加入鍵值的順序有關。
但是調(diào)用keys方法時，返回值不考慮順序。
dic['k2'] = 'v1'
dic['k1'] = 'v2'
dic2 = OrderedDict()
dic2['k1'] = 'v2'
dic2['k2'] = 'v1'
print(dic.keys() == dic2.keys())
print(dic == dic2)
dt = {'k2': 'v1', 'k1': 'v2'}
dt2 = {'k1': 'v2', 'k2': 'v1'}
print(dt.keys() == dt2.keys())
print(dt == dt2)
"""
輸出:
True
False
True
True
"""
