Python中字典(dict)和列表(list)的排序方法实例
一、对列表(list)进行排序
推荐的排序方式是使用内建的sort()方法,速度最快而且属于稳定排序
>>> a = [1,9,3,7,2,0,5]
>>> a.sort()
>>> print a
[0, 1, 2, 3, 5, 7, 9]
>>> a.sort(reverse=True)
>>> print a
[9, 7, 5, 3, 2, 1, 0]
>>> b = ['e','a','be','ad','dab','dbc']
>>> b.sort()
>>> print b
['a', 'ad', 'be', 'dab', 'dbc', 'e']
对列表的排序是遵循DSU(decorate-sort-undecorate)模式的,序列是安装条目的顺序进行比较的,对刚刚例子中的字符串来说,就是按照从左到右的顺序,逐个字符进行比较,一旦得出结果就停止比较。
二、对字典(dict)进行排序
其实字典(dict)是一个无序序列,谈不上排序,我们只能按照字典的键/值进行排序,然后让对应值/键也处于同样的顺序
任何对字典的排序问题,都要最终归结为对字典(dict)的键(key)或者值(value)组成的列表(list)的排序
1、按字典(dict)的键进行排序[1]
def sortedDictValues(adict,reverse=False):
keys = adict.keys()
keys.sort(reverse=reverse)
return [adict[key] for key in keys]
如果需要同时返回键和值的话,之用将最后的return语句改为:
还有一种书写简单的方法,就是使用内置的sorted()方法进行排序:
>>> d = {'c':1,'e':'5','b':7}
>>> sorted(d.items())
[('b', 7), ('c', 1), ('e', '5')]
不过性能会有些许的下降,如果很苛求性能,还是使用原生对list.sort()方法比较好
2、按字典(dict)的值进行排序[2]
def sorted_dict(container, keys, reverse):
"""返回 keys 的列表,根据container中对应的值排序"""
aux = [ (container[k], k) for k in keys]
aux.sort()
if reverse: aux.reverse()
return [k for v, k in aux]
同样可以用sorted()方法实现同样的功能:
三、结语
通过以上代码的分析,大致总结处以下几条原则:
* 对字典的排序,最终都要归结为对字典的键或者值组成的列表的排序
* 对列表的排序,优先使用内置的list.sort()方法

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