使用另一个包含Python长度的列表拆分列表

Question

注意:根据某些人的建议,我将此问题转发给codereview网站

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我想使用包含每个拆分长度的另一个列表拆分列表.

例如.

>>> print list(split_by_lengths(list('abcdefg'), [2,1]))
... [['a', 'b'], ['c'], ['d', 'e', 'f', 'g']]
>>> print list(split_by_lengths(list('abcdefg'), [2,2]))
... [['a', 'b'], ['c', 'd'], ['e', 'f', 'g']]    
>>> print list(split_by_lengths(list('abcdefg'), [2,2,6]))
... [['a', 'b'], ['c', 'd'], ['e', 'f', 'g']]
>>> print list(split_by_lengths(list('abcdefg'), [1,10]))
... [['a'], ['b', 'c', 'd', 'e', 'f', 'g']]
>>> print list(split_by_lengths(list('abcdefg'), [2,2,6,5]))
... [['a', 'b'], ['c', 'd'], ['e', 'f', 'g']]

您可以注意到,如果长度列表未涵盖所有列表,则我将其余元素作为附加子列表附加.此外,我希望在长度列表产生更多要分割的列表中的元素的情况下,最后避免空列表.

我已经有一个按我想要的功能:

def take(n, iterable):
    "Return first n items of the iterable as a list"
    return list(islice(iterable, n))

def split_by_lengths(list_, lens):
    li = iter(list_)
    for l in lens:
        elems = take(l,li)
        if not elems:
            break
        yield elems
    else:
        remaining = list(li)
        if remaining:
           yield remaining

但是我想知道是否有更多的pythonic方法来编写一个函数.

注意:我take(n, iterable)从Itertools食谱中抓取:

Answer 1

你可以这样做itertools.islice:

from itertools import islice

def split_by_lengths(seq, num):
    it = iter(seq)
    for x in num:
        out = list(islice(it, x))
        if out:
            yield out
        else:
            return   #StopIteration 
    remain = list(it)
    if remain:
        yield remain

演示:

>>> list(split_by_lengths(list('abcdefg'), [2,1]))
[['a', 'b'], ['c'], ['d', 'e', 'f', 'g']]
>>> list(split_by_lengths(list('abcdefg'), [2,2]))
[['a', 'b'], ['c', 'd'], ['e', 'f', 'g']]
>>> list(split_by_lengths(list('abcdefg'), [2,2,6]))
[['a', 'b'], ['c', 'd'], ['e', 'f', 'g']]
>>> print list(split_by_lengths(list('abcdefg'), [1,10]))
[['a'], ['b', 'c', 'd', 'e', 'f', 'g']]

上述版本的较短版本,但请注意,与第一个答案不同,一旦迭代器耗尽,这将不会短路.

def split_by_lengths(seq, num):
    it = iter(seq)
    out =  [x for x in (list(islice(it, n)) for n in num) if x]
    remain = list(it)
    return out if not remain else out + [remain]