(1) os.system

仅仅在一个子终端运行系统命令，而不能获取命令执行后的返回信息

system(command) -> exit_status 

Execute the command (a string) in a subshell.

如果再命令行下执行，结果直接打印出来

>>> os.system('ls')

04101419778.CHM   bash      document    media      py-django   video

11.wmv            books     downloads   Pictures  python

all-20061022      Desktop   Examples    project    tools

(2) os.popen

该方法不但执行命令还返回执行后的信息对象

popen(command [, mode='r' [, bufsize]]) -> pipe 

Open a pipe to/from a command returning a file object.

例如：

>>>tmp = os.popen('ls *.py').readlines()

>>>tmp

Out[21]:

['dump_db_pickle.py ',

'dump_db_pickle_recs.py ',

'dump_db_shelve.py ',

'initdata.py ',

'__init__.py ',

'make_db_pickle.py ',

'make_db_pickle_recs.py ',

'make_db_shelve.py ',

'peopleinteract_query.py ',

'reader.py ',

'testargv.py ',

'teststreams.py ',

'update_db_pickle.py ',

'writer.py ']

好处在于：将返回的结果赋于一变量，便于程序的处理。

(3) 使用模块 subprocess

>>> import subprocess

>>> subprocess.call(["cmd", "arg1", "arg2"],shell=True)

获取返回和输出:

import subprocess

p = subprocess.Popen('ls', shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

for line in p.stdout.readlines():

    print line,

retval = p.wait()

(4) 使用模块 commands

>>> import commands

>>> dir(commands)

['__all__', '__builtins__', '__doc__', '__file__', '__name__', 'getoutput', 'getstatus','getstatusoutput', 'mk2arg', 'mkarg']

>>> commands.getoutput("date")

'Wed Jun 10 19:39:57 CST 2009'

>>>

>>> commands.getstatusoutput("date")

(0, 'Wed Jun 10 19:40:41 CST 2009')

注意： 当执行命令的参数或者返回中包含了中文文字，那么建议使用subprocess，如果使用os.popen则会出现下面的错误:

Traceback (most recent call last):

  File "./test1.py", line 56, inmain()

  File "./test1.py", line 45, in main

    fax.sendFax()

  File "./mailfax/Fax.py", line 13, in sendFax

    os.popen(cmd)

UnicodeEncodeError: 'ascii' codec can't encode characters in position 46-52: ordinal not inrange(128)