分裂Python中的txt文件行

我有。txt文件格式为:

x1 x2 x3 y1 y2 y3 z1 z2 z3
x1 x2 x3 y1 y2 y3 z1 z2 z3

例如:

   1.9849207e-01   1.9993099e-01   2.0150793e-01   9.6169322e-02   9.6354487e-02   1.0630896e-01   1.5000000e-02   1.6090730e-02   1.5000000e-02
   1.9993099e-01   2.0261176e-01   2.0150793e-01   9.6354487e-02   1.0536750e-01   1.0630896e-01   1.6090730e-02   1.6090730e-02   1.5000000e-02

我使用了以下剪报:

from itertools import *

with open('path/snip.txt', 'r') as f_input, open('path/snip_output.txt', 'w') as f_output:
    values = []
    for line in f_input:
        values.extend(line.split())

    ivalues = iter(values)

    for triple in iter(lambda: list(islice(ivalues, 3)), []):
        f_output.write(' '.join(triple) + '\n')

得到:

x1 x2 x3
y1 y2 y3
z1 z2 z3
x1 x2 x3
y1 y2 y3
z1 z2 z3

然而,以下是我想要的,但我不知道如何在islice中处理两个步骤:

x1 y1 z1
x2 y2 z2
x3 y3 z3
x1 y1 z1
x2 y2 z2
x3 y3 z3