split作用：把字符串变成列表，这个字符串必须是多行文字。如果是单行文字或一个单词是不行的，实例操作如下：
In [46]: output=subprocess.check_output(['df','-h'])
In [60]: print(output)
b'Filesystem Size Used Avail Use% Mounted on\n/dev/mapper/centos-root 48G 7.6G 40G 16% /\ndevtmpfs 1.9G 0 1.9G 0% /dev\ntmpfs 1.9G 0 1.9G 0% /dev/shm\ntmpfs 1.9G 20M 1.9G 2% /run\ntmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup\n/dev/sda1 1014M 142M 873M 14% /boot\n/dev/mapper/centos-home 23G 40M 23G 1% /home\ntmpfs 1.9G 12K 1.9G 1% /var/lib/kubelet/pods/5cdc5bde-23a2-11e9-8321-000c2935f634/volumes/kubernetes.io~secret/flannel-token-smd42\noverlay 48G 7.6G 40G 16% /var/lib/docker/overlay/5e0d6edc162c3d5e1465e8cb69426423f27b74acbf2cb984fc012acbe0f804f0/merged\nshm 64M 0 64M 0% /var/lib/docker/containers/9c450ecf4d7b750fef3a00f92a7a9a2c536df52041e04546c2350566f1e90206/shm\noverlay 48G 7.6G 40G 16% /var/lib/docker/overlay/1932a1a32f66d39708a632c5e2b767ae5024484350ff7aa6072f46ad65393e1f/merged\ntmpfs 378M 0 378M 0% /run/user/0\n'
In [56]: lines=output.decode('utf8').split('\n')
In [57]: lines
Out[57]:
['Filesystem Size Used Avail Use% Mounted on',
'/dev/mapper/centos-root 48G 7.6G 40G 16% /',
'devtmpfs 1.9G 0 1.9G 0% /dev',
'tmpfs 1.9G 0 1.9G 0% /dev/shm',
'tmpfs 1.9G 20M 1.9G 2% /run',
'tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup',
'/dev/sda1 1014M 142M 873M 14% /boot',
'/dev/mapper/centos-home 23G 40M 23G 1% /home',
'tmpfs 1.9G 12K 1.9G 1% /var/lib/kubelet/pods/5cdc5bde-23a2-11e9-8321-000c2935f634/volumes/kubernetes.io~secret/flannel-token-smd42',
'overlay 48G 7.6G 40G 16% /var/lib/docker/overlay/5e0d6edc162c3d5e1465e8cb69426423f27b74acbf2cb984fc012acbe0f804f0/merged',
'shm 64M 0 64M 0% /var/lib/docker/containers/9c450ecf4d7b750fef3a00f92a7a9a2c536df52041e04546c2350566f1e90206/shm',
'overlay 48G 7.6G 40G 16% /var/lib/docker/overlay/1932a1a32f66d39708a632c5e2b767ae5024484350ff7aa6072f46ad65393e1f/merged',
'tmpfs 378M 0 378M 0% /run/user/0',
'']
In [58]: for line in lines[1:-1]:
...: if line:
...: print(line.split()[-2])
...:
16%
0%
0%
2%
0%
14%
1%
1%
16%
0%
16%
0%
