如何访问字典中的第一个和最后一个元素? [英] How to access the first and the last elements in a dictionary?

问题描述

发布之前，我已经经历过>访问字典中的任意元素在Python中，但对此我不确定.

Before posting, I have already gone through Access an arbitrary element in a dictionary in Python, butI'm uncertain about this.

我有一个很长的字典，我必须获取它的第一个和最后一个键的值.我可以使用dict[dict.keys()[0]]和dict[dict.keys()[-1]]来获取第一个和最后一个元素，但是由于key:value对是以随机形式输出的(如key:value对的位置是随机的)，将提供解决方案吗在此链接中始终有效吗?

I have a long dictionary and I've to get the values of its first and last keys. I can use dict[dict.keys()[0]] and dict[dict.keys()[-1]] to get the first and last elements, but since the key:value pairs are outputted in a random form(as in the positioning of the key:value pairs is random), will the solution provided in this link always work?

推荐答案

使用

Use an OrderedDict, because a normal dictionary doesn't preserve the insertion order of its elements when traversing it. Here's how:

# import the right class
from collections import OrderedDict

# create and fill the dictionary
d = OrderedDict()
d['first']  = 1
d['second'] = 2
d['third']  = 3

# retrieve key/value pairs
els = list(d.items()) # explicitly convert to a list, in case it's Python 3.x

# get first inserted element 
els[0]
=> ('first', 1)

# get last inserted element 
els[-1]
=> ('third', 3)

这篇关于如何访问字典中的第一个和最后一个元素?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！