如何将任意长度的列表拆分为大小相等的块?


请参阅如果数据结果将直接用于循环,并且不需要存储,则如何以块形式遍历列表。

对于字符串输入的同一问题,请参见每n个字符拆分字符串?。相同的技术通常适用,但也有一些变化。


当前回答

呵呵,单行版本

In [48]: chunk = lambda ulist, step:  map(lambda i: ulist[i:i+step],  xrange(0, len(ulist), step))

In [49]: chunk(range(1,100), 10)
Out[49]: 
[[1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
 [11, 12, 13, 14, 15, 16, 17, 18, 19, 20],
 [21, 22, 23, 24, 25, 26, 27, 28, 29, 30],
 [31, 32, 33, 34, 35, 36, 37, 38, 39, 40],
 [41, 42, 43, 44, 45, 46, 47, 48, 49, 50],
 [51, 52, 53, 54, 55, 56, 57, 58, 59, 60],
 [61, 62, 63, 64, 65, 66, 67, 68, 69, 70],
 [71, 72, 73, 74, 75, 76, 77, 78, 79, 80],
 [81, 82, 83, 84, 85, 86, 87, 88, 89, 90],
 [91, 92, 93, 94, 95, 96, 97, 98, 99]]

其他回答

a = [1, 2, 3, 4, 5, 6, 7, 8, 9]
CHUNK = 4
[a[i*CHUNK:(i+1)*CHUNK] for i in xrange((len(a) + CHUNK - 1) / CHUNK )]

我意识到这个问题已经过时了(在谷歌上被它绊倒了),但肯定像下面这样的问题比任何复杂的建议都要简单和清晰得多,而且只使用切片:

def chunker(iterable, chunksize):
    for i,c in enumerate(iterable[::chunksize]):
        yield iterable[i*chunksize:(i+1)*chunksize]

>>> for chunk in chunker(range(0,100), 10):
...     print list(chunk)
... 
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
[20, 21, 22, 23, 24, 25, 26, 27, 28, 29]
... etc ...

我在这个问题的副本中看到了最棒的Python式答案:

from itertools import zip_longest

a = range(1, 16)
i = iter(a)
r = list(zip_longest(i, i, i))
>>> print(r)
[(1, 2, 3), (4, 5, 6), (7, 8, 9), (10, 11, 12), (13, 14, 15)]

您可以为任何n创建n元组。如果a=范围(1,15),那么结果将是:

[(1, 2, 3), (4, 5, 6), (7, 8, 9), (10, 11, 12), (13, 14, None)]

如果列表被平均划分,那么可以用zip替换zip_langest,否则三元组(13、14、None)将丢失。上面使用了Python 3。对于Python 2,请使用izip_length。

由于我必须这样做,下面是我的解决方案,给出了一个生成器和一个批量大小:

def pop_n_elems_from_generator(g, n):
    elems = []
    try:
        for idx in xrange(0, n):
            elems.append(g.next())
        return elems
    except StopIteration:
        return elems

抽象将是

l = [1,2,3,4,5,6,7,8,9]
n = 3
outList = []
for i in range(n, len(l) + n, n):
    outList.append(l[i-n:i])

print(outList)

这将打印:

[[1, 2, 3], [4, 5, 6], [7, 8, 9]]