回答问题

我有一个列表,它由以下元素组成,

list1 = [a1,a2,a3]

该列表的每个元素本身可以是可变大小的列表,例如,

a1 = [x1,y1,z1], a2 = [w2,x2,y2,z2], a3 = [p3,r3,t3,n3]

设置一个遍历 list1 并产生每个元素的组成部分的生成器对我来说是直截了当的;

array = []
for i in list1:
    for j in i:
        array.append[j]
        yield array

但是,有没有办法这样做,所以我可以指定数组的大小?

例如 - 批量大小为两个;

1st yield : [x1,y1]
2nd yield : [z1,w1]
3rd yield : [x2,y2]
4th yield : [z2,p3]
5th yield : [r3,t3]
6th yield : [n3]
7th yield : repeat 1st

或批量大小为 4;

1st yield : [x1,y1,z1,w1]
2nd yield : [x2,y2,z2,p3]
3rd yield : [r3,t3,n3]
4th yield : repeat first

对于不同大小的列表执行此操作似乎并不简单,每个列表都包含其他不同大小的列表。

Answers

这很容易,实际上,使用itertools:

>>> a1 = ['x1','y1','z1']; a2 = ['w2','x2','y2','z2']; a3 = ['p3','r3','t3','n3']
>>> list1 = [a1,a2,a3]
>>> from itertools import chain, islice
>>> flatten = chain.from_iterable
>>> def slicer(seq, n):
...     it = iter(seq)
...     return lambda: list(islice(it,n))
...
>>> def my_gen(seq_seq, batchsize):
...     for batch in iter(slicer(flatten(seq_seq), batchsize), []):
...         yield batch
...
>>> list(my_gen(list1, 2))
[['x1', 'y1'], ['z1', 'w2'], ['x2', 'y2'], ['z2', 'p3'], ['r3', 't3'], ['n3']]
>>> list(my_gen(list1, 4))
[['x1', 'y1', 'z1', 'w2'], ['x2', 'y2', 'z2', 'p3'], ['r3', 't3', 'n3']]

注意,我们可以在 Python 3.3+ 中使用yield from:

>>> def my_gen(seq_seq, batchsize):
...   yield from iter(slicer(flatten(seq_seq), batchsize), [])
...
>>> list(my_gen(list1,2))
[['x1', 'y1'], ['z1', 'w2'], ['x2', 'y2'], ['z2', 'p3'], ['r3', 't3'], ['n3']]
>>> list(my_gen(list1,3))
[['x1', 'y1', 'z1'], ['w2', 'x2', 'y2'], ['z2', 'p3', 'r3'], ['t3', 'n3']]
>>> list(my_gen(list1,4))
[['x1', 'y1', 'z1', 'w2'], ['x2', 'y2', 'z2', 'p3'], ['r3', 't3', 'n3']]
>>>