滚动或滑动窗口迭代器？

问题描述

我需要在序列/迭代器/生成器上可迭代的滚动窗口（又称滑动窗口）。默认的Python迭代可以视为一种特殊情况，窗口长度为1。我目前正在使用以下代码。有没有人有更Pythonic，更简单或更有效的方法来做到这一点？

I need a rolling window (aka sliding window) iterable over a sequence/iterator/generator. Default Python iteration can be considered a special case, where the window length is 1. I'm currently using the following code. Does anyone have a more Pythonic, less verbose, or more efficient method for doing this?

def rolling_window(seq, window_size):
    it = iter(seq)
    win = [it.next() for cnt in xrange(window_size)] # First window
    yield win
    for e in it: # Subsequent windows
        win[:-1] = win[1:]
        win[-1] = e
        yield win

if __name__=="__main__":
    for w in rolling_window(xrange(6), 3):
        print w

"""Example output:

   [0, 1, 2]
   [1, 2, 3]
   [2, 3, 4]
   [3, 4, 5]
"""

推荐答案

老版本的Python文档中有一个带有：

There's one in an old version of the Python docs with itertools examples:

from itertools import islice

def window(seq, n=2):
    "Returns a sliding window (of width n) over data from the iterable"
    "   s -> (s0,s1,...s[n-1]), (s1,s2,...,sn), ...                   "
    it = iter(seq)
    result = tuple(islice(it, n))
    if len(result) == n:
        yield result
    for elem in it:
        result = result[1:] + (elem,)
        yield result

文档中的结果更为简洁，使用 itertools 产生更大的效果。

The one from the docs is a little more succinct and uses itertools to greater effect I imagine.

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