python中的有序字典及其使用方法

d1={}

d1['a']='a'
d1['b']='b'
d1['c']='c'
d1['d']='d'   #此時的d1 = 
for k,v in d1.items():
print k,v

a a

c cb b
d d

import collections

d1={}
d1=collections.ordereddict()  #將普通字典轉換為有序字典
d1['a']='a'
d1['b']='b'
d1['c']='c'
d1['d']='d'
for k,v in d1.items():
print k,v

a a

b bc c
d d

上面兩個例子之所以字典中插入元素，而不是一開始就將字典中的元素定義好，是因為有序字典的作用只是記住元素插入順序並按順序輸出。

如果有序字典中的元素一開始就定義好了，後面沒有插入元素這一動作，那麼遍歷有序字典，其輸出結果為空，因為缺少了有序插入這一條件，所以此時有序字典就失去了作用，所以有序字典一般用於動態新增並需要按新增順序輸出的時候。

舉例說明：

import collections

d2 = 
d2=collections.ordereddict()  #將普通字典轉換為有序字典
for k,v in d2.items():
print k,v

建立有序字典

import collections

dic = collections.ordereddict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic)
#輸出：ordereddict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')])

import collections

dic = collections.ordereddict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic.clear()
print(dic)
#輸出：ordereddict()

import collections

dic = collections.ordereddict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
new_dic = dic.copy()
print(new_dic)
#輸出：ordereddict([('k1', 'v1'), ('k2', 'v2')])

import collections

dic = collections.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)])

import collections

dic = collections.ordereddict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
print(dic.items())
#輸出：odict_items([('k1', 'v1'), ('k2', 'v2')])

import collections

dic = collections.ordereddict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
print(dic.keys())
# 輸出：odict_keys(['k1', 'k2'])

import collections

dic = collections.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')])

import collections

dic = collections.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')])

import collections

dic = collections.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')])

import collections

dic = collections.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)])

import collections

dic = collections.ordereddict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic.values())
# 輸出：odict_values(['v1', 'v2', 'v3'])

python中的有序字典OrderedDict

1.ordereddict 有序字典 ordereddict是dict的子類，它記住了內容新增的順序。比較時，ordereddict要內容和順序完全相同才會視為相等。python view plain copy import collections d collections.ordereddict...

python的有序字典

字典即雜湊表，由空間換取時間得到取數o 1 的速度。對於雜湊表有乙個很好的比喻就是櫃子，每乙個物件通過計算獲取乙個hash值，hash值就像是櫃子的編號 字典的key 用以迅速的查詢櫃子裡所儲存的東西 字典的value 如果櫃子裡有多個東西 hash值不唯一 根據具體演算法的實現方式有不同的處理方式...

Python有序字典

最近的django開發中用到了有序字典，所以研究了一下，以下。示例 有序字典和通常字典類似，只是它可以記錄元素插入其中的順序，而一般字典是會以任意的順序迭代的。普通字典 1 d1 2 d1 a a 3 d1 b b 4 d1 c c 5 d1 d d 此時的d1 6 for k,v in d1.it...