Subprocess.Popen() 使用问题解决方案

from subprocess import Popen,PIPE

1.光标处于闪烁等待状态，不能实时输出测试cmd界面.

[原因]：使用communicate()函数，需要等脚本执行完才返回。

def communicate(self, input=None):

    """Interact with process: Send data to stdin.  Read data from stdout and stderr, until end-of-file is reached.  Wait for process to terminate.  
    The optional input argument should be a string to be sent to the child process, or None, if no data should be sent to the child.

    communicate() returns a tuple (stdout, stderr).
    """

[方案]：用subprocess.poll()函数替代, 程序运行完毕后返回1. 否则为None/0.

def poll(self):
    """Check if child process has terminated. Set and return returncode attribute."""
    return self._internal_poll()

2. 输出结果没有换行,一大坨...
[原因]: 未使用
[方案]： 使用while 循环结合readline + poll() 函数, 出来一行打印一行.... stdout.readline() 


Fail 代码：

1         p1 = Popen(['bash.exe', 'run_all_tests.sh', 'win32'], stdout=PIPE, shell=True)
2         print repr(p1.communicate()[0])  #communicate 函数

PASS 代码：


#  
1         p1 = Popen(['bash.exe', 'run_all_tests.sh', 'win32'], stdout=subprocess.PIPE, shell=True)
2         while p1.poll() is None:
3             data = p1.stdout.readline()
4             print data
5         #print repr(p1.communicate()[0])

''' # 下面多了层循环，为一个个字符打印 xxx
 3         while p1.poll() is None:
 4             for line in p1.stdout.readline():
 5                 print line
 6         '''

3.传递系统变量env path 的两种方式.

3.1 模仿命令行，windows 用 set 去设置

3.2 [推荐] 不适用set 命令行，直接传递my_env 参数到subpross.Popen()类初始化. 这样可以有效避免字符串转义符号的问题

查看Popen 类帮助文档如下

 1 class Popen(object):
 2     """ Execute a child program in a new process.
 3 
 4     For a complete description of the arguments see the Python documentation.
 5 
 6     Arguments:
 7       args: A string, or a sequence of program arguments.
 8 
 9       bufsize: supplied as the buffering argument to the open() function when
10           creating the stdin/stdout/stderr pipe file objects
11 
12       executable: A replacement program to execute.
13 
14       stdin, stdout and stderr: These specify the executed programs' standard
15           input, standard output and standard error file handles, respectively.
16 
17       preexec_fn: (POSIX only) An object to be called in the child process
18           just before the child is executed.
19 
20       close_fds: Controls closing or inheriting of file descriptors.
21 
22       shell: If true, the command will be executed through the shell.
23 
24       cwd: Sets the current directory before the child is executed.
25 
26       env: Defines the environment variables for the new process.
27 
28       universal_newlines: If true, use universal line endings for file
29           objects stdin, stdout and stderr.
30 
31       startupinfo and creationflags (Windows only)
32 
33     Attributes:
34         stdin, stdout, stderr, pid, returncode
35     """
36     _child_created = False  # Set here since __del__ checks it
37 
38     def __init__(self, args, bufsize=0, executable=None,
39                  stdin=None, stdout=None, stderr=None,
40                  preexec_fn=None, close_fds=False, shell=False,
41                  cwd=None, env=None, universal_newlines=False,
42                  startupinfo=None, creationflags=0):
43         """Create new Popen instance."""

View Code

所以代码加入参数即可：

1 p1 = Popen(['bash.exe', 'run_all_tests.sh', 'win32'], stdout=PIPE, shell=True, env=my_env)

Subprocess.Popen() 使用问题解决方案

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