Python subprocess shell 编程规范

　　使用subprocess通过shell调用另一个模块组件时，需要对返回的code进行判断。判断结果为执行失败时需要raise Exception，不然调用树过于复杂时，我们很难跟踪到异常发生的位置。sys.exit(1)虽然也可以达到对执行结果进行判断的目的，但是它难于追踪异常发生的位置。

a.py
`-- b.py
    `-- ls

a.py

import sys, subprocess

def exec_cmd(cmd):
    """Run shell command"""
    p = subprocess.Popen(cmd,stdin = subprocess.PIPE, 
        stdout = subprocess.PIPE,
        stderr = subprocess.STDOUT,
        shell = True)

    log_content = p.communicate()[0]

    return p.returncode, log_content

def main():
    cmd = "python b.py"
    cmd_code, cmd_log = exec_cmd(cmd)
    if not cmd_code == 0:
        raise Exception(cmd_log)

if __name__ == '__main__':
    main()

b.py

import sys, subprocess

def exec_cmd(cmd):
    """Run shell command"""
    p = subprocess.Popen(cmd,stdin = subprocess.PIPE, 
        stdout = subprocess.PIPE,
        stderr = subprocess.STDOUT,
        shell = True)

    log_content = p.communicate()[0]

    return p.returncode, log_content

def main():
    cmd = """ls c.py"""
    cmd_code, cmd_log = exec_cmd(cmd)
    if not cmd_code == 0:
        raise Exception(cmd_log)

if __name__ == '__main__':
    main()

运行结果：

waterforestdeiMac:pythonCrawler waterforest$ python a.py 
Traceback (most recent call last):
  File "a.py", line 21, in <module>
    main()
  File "a.py", line 18, in main
    raise Exception(cmd_log)
Exception: Traceback (most recent call last):
  File "b.py", line 21, in <module>
    main()
  File "b.py", line 18, in main
    raise Exception(cmd_log)
Exception: ls: c.py: No such file or directory


waterforestdeiMac:pythonCrawler waterforest$