Python常用外部指令执行代码实例

1、os.system()

阻塞

屏幕会打印命令的输出

返回命令结果码

# -*- encoding=utf-8 -*-
import os
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  ret1 = os.system(\'python\')
  print(\'ret1:{}\'.format(ret1))
  ret2 = os.system(\'java -version\')
  print(\'ret2:{}\'.format(ret2))
  print(\'结束\')

运行

可能有人理解阻塞是因为运行了python，因此我尝试两个命令都用java -version

# -*- encoding=utf-8 -*-

import os

if __name__ == \'__main__\':
  pass
  print(\'开始\')
  ret1 = os.system(\'java -version\')
  print(\'ret1:{}\'.format(ret1))
  ret2 = os.system(\'java -version\')
  print(\'ret2:{}\'.format(ret2))
  print(\'结束\')

运行

2、os.popen()

阻塞或不阻塞

屏幕不会打印出命令的输出

返回文件对象，可用read,readline读取

不阻塞时：

# -*- encoding=utf-8 -*-
import os
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  os.popen(\'python\')
  ret2 = os.popen(\'java -version\')
  print(\'结束\')

运行（程序很快打印开始和结束，就像只用了两个print语句一样快）

阻塞时：

# -*- encoding=utf-8 -*-
import os
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  ret1 = os.popen(\'python\')
  print(ret1.read())
  ret2 = os.popen(\'java -version\')
  print(ret2.read())
  print(\'结束\')

运行

3、commands.getstatusoutput

python2.+中使用

需要到linux运行

阻塞或者非阻塞

屏幕不会打印出命令的输出

非阻塞时

# -*- encoding=utf-8 -*-
import commands
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  ret1 = commands.getstatusoutput(\'python\')
  ret2 = commands.getstatusoutput(\'java -version\')
  print(\'结束\')

运行

阻塞时:

# -*- encoding=utf-8 -*-
import commands
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  ret1 = commands.getstatusoutput(\'python\')
  print ret1[0]
  print ret1[1]
  print \'==============\'
  ret2 = commands.getstatusoutput(\'java -version\')
  print ret2[0]
  print ret2[1]
  print \'==============\'
  print(\'结束\')

运行

4、subprocess中Popen

阻塞或非阻塞，同上面一样，通过是否读取IO决定是否阻塞

屏幕会打印出命令的输出

可通过stdout，stderr参数指定输出或错误打印到文件

# -*- encoding=utf-8 -*-
import subprocess
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  s1 = subprocess.Popen(\'python\')
  s1.wait()
  s2 = subprocess.Popen(\'java -version\')
  s2.wait()
  print(\'结束\')

运行

4.1、输出到文件

通过文件对象来输出到文件中

# -*- encoding=utf-8 -*-
import subprocess
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  with open(\'s1.txt\', \'w\') as f:
    s1 = subprocess.Popen(\'python\', stdout=f, ) # 指定输出重定向到文件
    s1.wait(10) # 超过10秒还没执行完会抛出异常
  with open(\'s2.txt\', \'w\') as f:
    s2 = subprocess.Popen(\'java -version\', stdout=f, stderr=f) # 指定输出和错误都重定向到文件
    s2.wait()
  print(\'结束\')

运行后可看到文件已经写入，屏幕不打印。需要注意是stdout还是stderr。

4.2、捕获输出和错误

PIPE通过开一个新的管道来接收运行状态

# -*- encoding=utf-8 -*-

import subprocess

if __name__ == \'__main__\':
  pass
  print(\'开始\')
  s1 = subprocess.Popen(\'java -version\', stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  s1.wait(10) # 超过10秒还没执行完会抛出异常
  print(s1.returncode) # 结果码
  print(s1.poll()) # 已经执行结束返回结果码，否则返回None
  std1 = s1.stdout.read()
  print(\'std_out:{}\'.format(std1))
  std2 = s1.stderr.read()
  print(\'std_err:{}\'.format(std2))
  print(\'结束\')

运行

5、subprocess.call

用来替代os.system

阻塞

# -*- encoding=utf-8 -*-
import subprocess
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  s1 = subprocess.call(\'java -version\', )
  print(s1)
  s2 = subprocess.call(\'python\', )
  print(s2)
  s3 = subprocess.call(\'python\', timeout=3) # 超时抛出异常
  print(s3)
  print(\'结束\')

6、check_call()和check_output()

都会检查结果码，不是0就抛出异常

check_call()返回状态码

check_output()返回输出

# -*- encoding=utf-8 -*-
import subprocess
if __name__ == \'__main__\':
  pass
  print(\'开始\')
  s1 = subprocess.check_call(\'java -version\', )
  print(s1)
  s2 = subprocess.check_output(\'java -version\', )
  print(s2)
  print(\'结束\')

运行