如果您需要从 Python 笔记本电脑(如 Jupyter、Zeppelin、Databricks 或 Google Cloud Datalab)中拨打一个支票命令,您只能使用! 预定。

例如,

!ls -ilF

在Python 3.5+中使用子过程,以下是我在Linux上做的技巧:

import subprocess

# subprocess.run() returns a completed process object that can be inspected
c = subprocess.run(["ls", "-ltrh"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
print(c.stdout.decode('utf-8'))

正如文档中提到的那样,PIPE 值是比特序列,为了正确显示它们,应考虑解码。

上述代码的结果是:

total 113M
-rwxr-xr-x  1 farzad farzad  307 Jan 15  2018 vpnscript
-rwxrwxr-x  1 farzad farzad  204 Jan 15  2018 ex
drwxrwxr-x  4 farzad farzad 4.0K Jan 22  2018 scripts
.... # Some other lines

从 OpenStack Neutron 中获取网络 ID:

#!/usr/bin/python
import os
netid = "nova net-list | awk '/ External / { print $2 }'"
temp = os.popen(netid).read()  /* Here temp also contains new line (\n) */
networkId = temp.rstrip()
print(networkId)

新网列表

+--------------------------------------+------------+------+
| ID                                   | Label      | CIDR |
+--------------------------------------+------------+------+
| 431c9014-5b5d-4b51-a357-66020ffbb123 | test1      | None |
| 27a74fcd-37c0-4789-9414-9531b7e3f126 | External   | None |
| 5a2712e9-70dc-4b0e-9281-17e02f4684c9 | management | None |
| 7aa697f5-0e60-4c15-b4cc-9cb659698512 | Internal   | None |
+--------------------------------------+------------+------+

印刷输出(networkId)

27a74fcd-37c0-4789-9414-9531b7e3f126

在 Windows 中,您只能输入子过程模块并运行外部命令,以下列方式呼叫 subprocess.Popen(), subprocess.Popen().communicate() 和 subprocess.Popen().wait():

# Python script to run a command line
import subprocess

def execute(cmd):
    """
        Purpose  : To execute a command and return exit status
        Argument : cmd - command to execute
        Return   : exit_code
    """
    process = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    (result, error) = process.communicate()

    rc = process.wait()

    if rc != 0:
        print "Error: failed to execute command:", cmd
        print error
    return result
# def

command = "tasklist | grep python"
print "This process detail: \n", execute(command)

出口:

This process detail:
python.exe                     604 RDP-Tcp#0                  4      5,660 K

>>> from subprocess import run
>>> from shlex import split
>>> completed_process = run(split('python --version'))
Python 3.8.8
>>> completed_process
CompletedProcess(args=['python', '--version'], returncode=0)

下面是最简单的使用的例子 - 它正如所要求的那样:

>>> from subprocess import run
>>> from shlex import split
>>> completed_process = run(split('python --version'))
Python 3.8.8
>>> completed_process
CompletedProcess(args=['python', '--version'], returncode=0)

>>> completed_process.args
['python', '--version']
>>> completed_process.returncode
0

如果您想捕获输出,您可以将 subprocess.PIPE 转移到适当的 stderr 或 stdout:

>>> from subprocess import PIPE
>>> completed_process = run(shlex.split('python --version'), stdout=PIPE, stderr=PIPE)
>>> completed_process.stdout
b'Python 3.8.8\n'
>>> completed_process.stderr
b''

相应的属性返回比特。

>>> import textwrap
>>> args = ['python', textwrap.__file__]
>>> cp = run(args, stdout=subprocess.PIPE)
>>> cp.stdout
b'Hello there.\n  This is indented.\n'

下面是源头的真实签名,如助(run)所示:

输入可以是一个字符串(或单码,如果指定编码或 universal_newlines=True)将被带到子过程的stdin。

这个 check=true 的例子比我可以看到的更好:

波恩

def __init__(self, args, bufsize=-1, executable=None,
             stdin=None, stdout=None, stderr=None,
             preexec_fn=None, close_fds=True,
             shell=False, cwd=None, env=None, universal_newlines=None,
             startupinfo=None, creationflags=0,
             restore_signals=True, start_new_session=False,
             pass_fds=(), *, user=None, group=None, extra_groups=None,
             encoding=None, errors=None, text=None, umask=-1, pipesize=-1):

了解Popen的剩余文档将作为读者的练习留下来。

最多案例:

在大多数情况下,一个短片的代码,如此,是你将需要的一切:

import subprocess
import shlex

source = "test.txt"
destination = "test_copy.txt"

base = "cp {source} {destination}'"
cmd = base.format(source=source, destination=destination)
subprocess.check_call(shlex.split(cmd))

它是干净和简单的。

subprocess.check_call 以论点运行命令,等待命令完成。 shlex.split 使用 shell-like syntax 分割行 cmd

其他案例:

如果这不适用于某些特定的命令,最有可能你有一个问题与命令线的解释器. 操作系统选择了默认一个不适合你的程序类型或可能没有找到适当的一个在系统可执行的路径。

例子:

使用Unix系统上的转向操作器

input_1 = "input_1.txt"
input_2 = "input_2.txt"
output = "merged.txt"
base_command = "/bin/bash -c 'cat {input} >> {output}'"

base_command.format(input_1, output=output)
subprocess.check_call(shlex.split(base_command))

base_command.format(input_2, output=output)
subprocess.check_call(shlex.split(base_command))

正如《Python Zen: Explicit is better than implicit》中所说的那样。

因此,如果使用 Python >=3.6 函数,它会看起来像这样:

import subprocess
import shlex

def run_command(cmd_interpreter: str, command: str) -> None:
    base_command = f"{cmd_interpreter} -c '{command}'"
    subprocess.check_call(shlex.split(base_command)