如何"减少"列表中的重复

Question

我无法想出减少列表中重复次数的最有效方法.

a = ['x','x','x','y','y','y','z','z','z','x','x','x','z','z','z','z','z','z']

期望的输出(如果我减少3组)将是:

a_reduced = ['x','y','z','x','z','z']

我想要循环遍历每个元素并做一个'[i]和[i + 1]和[i + 2]条件'的事情,但我确信有一种超级简单有效的方法来实现这一目标,而且我是只是缺少一些东西 请帮助,谢谢!

Answer 1

如果你的重复总是以3组为单位,你可以简单地做:

a = ['x','x','x','y','y','y','z','z','z','x','x','x','z','z','z','z','z','z']
a_reduced = a[::3]
print a_reduced
>>>['x', 'y', 'z', 'x', 'z', 'z']

这将只从列表中获取每个第3个元素.同样,这假设您的列表总是以3组为单位.如果不是,则会出现偏差.否则,如果你只想浓缩所有独特的重复,你可以使用itertools.groupby哪个会做到这一点:

from itertools import groupby
a = ['x','x','x','y','y','y','z','z','z','x','x','x','z','z','z','z','z','z']
a_reduced = [item[0] for item in groupby(a)]
print a_reduced
>>>['x', 'y', 'z', 'x', 'z']