python OrderedDict类（有序字典）

创建有序字典

import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic)

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

clear(清空有序字典)

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'''
import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic.clear()
print(dic)

#输出：OrderedDict()

copy(拷贝)

import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
new_dic = dic.copy()
print(new_dic)

#输出：OrderedDict([('k1', 'v1'), ('k2', 'v2')])

fromkeys(指定一个列表，把列表中的值作为字典的key,生成一个字典)

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'''
import collections

dic = collections.OrderedDict()
name = ['tom','lucy','sam']
print(dic.fromkeys(name))
print(dic.fromkeys(name,20))

#输出：OrderedDict([('tom', None), ('lucy', None), ('sam', None)])
#     OrderedDict([('tom', 20), ('lucy', 20), ('sam', 20)])

items(返回由“键值对组成元素“的列表)

import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
print(dic.items())

#输出：odict_items([('k1', 'v1'), ('k2', 'v2')])

keys(获取字典所有的key)

import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
print(dic.keys())

# 输出：odict_keys(['k1', 'k2'])

move_to_end(指定一个key，把对应的key-value移到最后)

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'''
import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
dic.move_to_end('k1')
print(dic)

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

pop(获取指定key的value，并在字典中删除)

import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
k = dic.pop('k2')
print(k,dic)

# 输出：v2 OrderedDict([('k1', 'v1'), ('k3', 'v3')])

popitem(按照后进先出原则，删除最后加入的元素，返回key-value)

import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic.popitem(),dic)
print(dic.popitem(),dic)

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

setdefault(获取指定key的value，如果key不存在，则创建)

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'''
import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
val = dic.setdefault('k5')
print(val,dic)

# 输出：None OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3'), ('k5', None)])

values(获取字典所有的value，返回一个列表)

import collections

dic = collections.OrderedDict()
dic['k1'] = 'v1'
dic['k2'] = 'v2'
dic['k3'] = 'v3'
print(dic.values())

# 输出：odict_values(['v1', 'v2', 'v3'])