2.4 版新增。
The subprocess 模块允许卵生新进程，连接到它们的输入/输出/错误管道，并获得它们的返回代码。此模块打算替换几个较旧的模块和函数：
os.system os.spawn* os.popen* popen2.* commands.*
Information about how this module can be used to replace the older functions can be found in the subprocess-replacements 章节。
另请参阅
POSIX users (Linux, BSD, etc.) are strongly encouraged to install and use the much more recent subprocess32 module instead of the version included with python 2.7. It is a drop in replacement with better behavior in many situations.
PEP 324 – PEP 提出 subprocess 模块
The recommended way to launch subprocesses is to use the following convenience functions. For more advanced use cases when these do not meet your needs, use the underlying Popen 接口。
运行的命令描述通过 args . Wait for command to complete, then return the returncode 属性。
The arguments shown above are merely the most common ones, described below in 经常使用的自变量 (hence the slightly odd notation in the abbreviated signature). The full function signature is the same as that of the Popen constructor - this functions passes all supplied arguments directly through to that interface.
范例：
>>> subprocess.call(["ls", "-l"]) 0 >>> subprocess.call("exit 1", shell=True) 1
警告
使用 shell=True can be a security hazard. See the warning under 经常使用的自变量 了解细节。
注意
不使用 stdout=PIPE or stderr=PIPE with this function as that can deadlock based on the child process output volume. Use Popen 采用 communicate() method when you need pipes.
Run command with arguments. Wait for command to complete. If the return code was zero then return, otherwise raise CalledProcessError 。 CalledProcessError object will have the return code in the returncode 属性。
The arguments shown above are merely the most common ones, described below in 经常使用的自变量 (hence the slightly odd notation in the abbreviated signature). The full function signature is the same as that of the Popen constructor - this functions passes all supplied arguments directly through to that interface.
范例：
>>> subprocess.check_call(["ls", "-l"]) 0 >>> subprocess.check_call("exit 1", shell=True) Traceback (most recent call last): ... subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1 Traceback (most recent call last): ... subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1
2.5 版新增。
警告
使用 shell=True can be a security hazard. See the warning under 经常使用的自变量 了解细节。
注意
不使用 stdout=PIPE or stderr=PIPE with this function as that can deadlock based on the child process output volume. Use Popen 采用 communicate() method when you need pipes.
Run command with arguments and return its output as a byte string.
If the return code was non-zero it raises a CalledProcessError 。 CalledProcessError object will have the return code in the returncode attribute and any output in the output 属性。
The arguments shown above are merely the most common ones, described below in 经常使用的自变量 (hence the slightly odd notation in the abbreviated signature). The full function signature is largely the same as that of the Popen constructor, except that stdout is not permitted as it is used internally. All other supplied arguments are passed directly through to the Popen 构造函数。
范例：
>>> subprocess.check_output(["echo", "Hello World!"]) 'Hello World!\n' >>> subprocess.check_output("exit 1", shell=True) Traceback (most recent call last): ... subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1 Traceback (most recent call last): ... subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1
To also capture standard error in the result, use stderr=subprocess.STDOUT :
>>> subprocess.check_output( ... "ls non_existent_file; exit 0", ... stderr=subprocess.STDOUT, ... shell=True) 'ls: non_existent_file: No such file or directory\n'
2.7 版新增。
警告
使用 shell=True can be a security hazard. See the warning under 经常使用的自变量 了解细节。
注意
不使用 stderr=PIPE with this function as that can deadlock based on the child process error volume. Use Popen 采用 communicate() method when you need a stderr pipe.
Special value that can be used as the stdin , stdout or stderr 自变量对于 Popen and indicates that a pipe to the standard stream should be opened.
Special value that can be used as the stderr 自变量对于 Popen and indicates that standard error should go into the same handle as standard output.
Exception raised when a process run by check_call() or check_output() 返回非零退出状态。
Exit status of the child process.
用于卵生子级进程的命令。
Output of the child process if this exception is raised by check_output() 。否则， None .
为支持各种使用案例， Popen constructor (and the convenience functions) accept a large number of optional arguments. For most typical use cases, many of these arguments can be safely left at their default values. The arguments that are most commonly needed are:
args is required for all calls and should be a string, or a sequence of program arguments. Providing a sequence of arguments is generally preferred, as it allows the module to take care of any required escaping and quoting of arguments (e.g. to permit spaces in file names). If passing a single string, either shell 必须为 True (see below) or else the string must simply name the program to be executed without specifying any arguments.
stdin , stdout and stderr specify the executed program’s standard input, standard output and standard error file handles, respectively. Valid values are PIPE , an existing file descriptor (a positive integer), an existing file object, and None . PIPE indicates that a new pipe to the child should be created. With the default settings of None , no redirection will occur; the child’s file handles will be inherited from the parent. Additionally, stderr 可以是 STDOUT , which indicates that the stderr data from the child process should be captured into the same file handle as for stdout.
当 stdout or stderr are pipes and universal_newlines is True then all line endings will be converted to '\n' as described for the 通用换行符 'U' mode argument to open() .
若 shell is True , the specified command will be executed through the shell. This can be useful if you are using Python primarily for the enhanced control flow it offers over most system shells and still want convenient access to other shell features such as shell pipes, filename wildcards, environment variable expansion, and expansion of ~ to a user’s home directory. However, note that Python itself offers implementations of many shell-like features (in particular, glob , fnmatch , os.walk() , os.path.expandvars() , os.path.expanduser() ，和 shutil ).
警告
Executing shell commands that incorporate unsanitized input from an untrusted source makes a program vulnerable to shell injection , a serious security flaw which can result in arbitrary command execution. For this reason, the use of shell=True is strongly discouraged in cases where the command string is constructed from external input:
>>> from subprocess import call >>> filename = input("What file would you like to display?\n") What file would you like to display? non_existent; rm -rf / # >>> call("cat " + filename, shell=True) # Uh-oh. This will end badly...
shell=False disables all shell based features, but does not suffer from this vulnerability; see the Note in the Popen constructor documentation for helpful hints in getting shell=False to work.
当使用 shell=True , pipes.quote() can be used to properly escape whitespace and shell metacharacters in strings that are going to be used to construct shell commands.
这些选项及所有其它选项的更详细描述在 Popen 构造函数文档编制。
此模块中底层进程的创建和管理的处理是通过 Popen 类。它提供了很大的灵活性，以便开发者能够处理方便函数未涵盖的不常见情况。
Execute a child program in a new process. On Unix, the class uses os.execvp() 类似行为来执行子级程序。在 Windows，类使用 Windows CreateProcess() 函数。自变量到 Popen 如下所示。
args should be a sequence of program arguments or else a single string. By default, the program to execute is the first item in args if args is a sequence. If args is a string, the interpretation is platform-dependent and described below. See the shell and executable arguments for additional differences from the default behavior. Unless otherwise stated, it is recommended to pass args as a sequence.
在 Unix，若 args is a string, the string is interpreted as the name or path of the program to execute. However, this can only be done if not passing arguments to the program.
注意
shlex.split() can be useful when determining the correct tokenization for args , especially in complex cases:
>>> import shlex, subprocess >>> command_line = raw_input() /bin/vikings -input eggs.txt -output "spam spam.txt" -cmd "echo '$MONEY'" >>> args = shlex.split(command_line) >>> print args ['/bin/vikings', '-input', 'eggs.txt', '-output', 'spam spam.txt', '-cmd', "echo '$MONEY'"] >>> p = subprocess.Popen(args) # Success!
Note in particular that options (such as -input ) and arguments (such as eggs.txt ) that are separated by whitespace in the shell go in separate list elements, while arguments that need quoting or backslash escaping when used in the shell (such as filenames containing spaces or the echo command shown above) are single list elements.
在 Windows，若 args is a sequence, it will be converted to a string in a manner described in 在 Windows 将自变量序列转换成字符串 . This is because the underlying CreateProcess() operates on strings.
The shell 自变量 (默认为 False ) specifies whether to use the shell as the program to execute. If shell is True , it is recommended to pass args as a string rather than as a sequence.
On Unix with shell=True , the shell defaults to /bin/sh 。若 args is a string, the string specifies the command to execute through the shell. This means that the string must be formatted exactly as it would be when typed at the shell prompt. This includes, for example, quoting or backslash escaping filenames with spaces in them. If args is a sequence, the first item specifies the command string, and any additional items will be treated as additional arguments to the shell itself. That is to say, Popen does the equivalent of:
Popen(['/bin/sh', '-c', args[0], args[1], ...])
在 Windows 采用 shell=True ， COMSPEC environment variable specifies the default shell. The only time you need to specify shell=True on Windows is when the command you wish to execute is built into the shell (e.g. dir or copy ). You do not need shell=True to run a batch file or console-based executable.
警告
传递 shell=True can be a security hazard if combined with untrusted input. See the warning under 经常使用的自变量 了解细节。
bufsize , if given, has the same meaning as the corresponding argument to the built-in open() function: 0 means unbuffered, 1 means line buffered, any other positive value means use a buffer of (approximately) that size. A negative bufsize means to use the system default, which usually means fully buffered. The default value for bufsize is 0 (unbuffered).
注意
If you experience performance issues, it is recommended that you try to enable buffering by setting bufsize to either -1 or a large enough positive value (such as 4096).
The executable argument specifies a replacement program to execute. It is very seldom needed. When shell=False , executable replaces the program to execute specified by args . However, the original args is still passed to the program. Most programs treat the program specified by args as the command name, which can then be different from the program actually executed. On Unix, the args name becomes the display name for the executable in utilities such as ps 。若 shell=True , on Unix the executable argument specifies a replacement shell for the default /bin/sh .
stdin , stdout and stderr specify the executed program’s standard input, standard output and standard error file handles, respectively. Valid values are PIPE , an existing file descriptor (a positive integer), an existing file object, and None . PIPE indicates that a new pipe to the child should be created. With the default settings of None , no redirection will occur; the child’s file handles will be inherited from the parent. Additionally, stderr 可以是 STDOUT , which indicates that the stderr data from the child process should be captured into the same file handle as for stdout.
若 preexec_fn is set to a callable object, this object will be called in the child process just before the child is executed. (Unix only)
若 close_fds is true, all file descriptors except 0 , 1 and 2 will be closed before the child process is executed. (Unix only). Or, on Windows, if close_fds is true then no handles will be inherited by the child process. Note that on Windows, you cannot set close_fds to true and also redirect the standard handles by setting stdin , stdout or stderr .
若 cwd 不是 None , the child’s current directory will be changed to cwd before it is executed. Note that this directory is not considered when searching the executable, so you can’t specify the program’s path relative to cwd .
若 env 不是 None , it must be a mapping that defines the environment variables for the new process; these are used instead of inheriting the current process’ environment, which is the default behavior.
注意
若指定， env 必须提供要执行程序要求的任何变量。在 Windows，为运行 并行汇编 指定 env must 包括有效 SystemRoot .
若 universal_newlines is True , the file objects stdout and stderr are opened as text files in 通用换行符 mode. Lines may be terminated by any of '\n' , the Unix end-of-line convention, '\r' , the old Macintosh convention or '\r\n' , the Windows convention. All of these external representations are seen as '\n' by the Python program.
注意
This feature is only available if Python is built with universal newline support (the default). Also, the newlines attribute of the file objects stdout , stdin and stderr are not updated by the communicate() method.
若给定， startupinfo 将是 STARTUPINFO 对象，会被传递给底层 CreateProcess 函数。 creationflags , if given, can be CREATE_NEW_CONSOLE or CREATE_NEW_PROCESS_GROUP . (Windows only)
Exceptions raised in the child process, before the new program has started to execute, will be re-raised in the parent. Additionally, the exception object will have one extra attribute called child_traceback , which is a string containing traceback information from the child’s point of view.
最常引发的异常是 OSError . This occurs, for example, when trying to execute a non-existent file. Applications should prepare for OSError 异常。
A ValueError 会被引发若 Popen is called with invalid arguments.
check_call() and check_output() 会引发 CalledProcessError if the called process returns a non-zero return code.
Unlike some other popen functions, this implementation will never call a system shell implicitly. This means that all characters, including shell metacharacters, can safely be passed to child processes. Obviously, if the shell is invoked explicitly, then it is the application’s responsibility to ensure that all whitespace and metacharacters are quoted appropriately.
实例化的 Popen 类具有下列方法：
校验子级进程是否已终止。设置并返回 returncode 属性。
等待子级进程终止。设置并返回 returncode 属性。
警告
这会死锁，当使用 stdout=PIPE and/or stderr=PIPE 子级进程生成足够输出到管道，这会阻塞等待的 OS 管道缓冲以接受更多数据。使用 communicate() to avoid that.
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() 返回元组 (stdoutdata, stderrdata) .
注意，若想要把数据发送给进程的 stdin，需要创建 Popen 对象采用 stdin=PIPE 。同样，要获取任何东西除了 None 在结果元组，需要给出 stdout=PIPE and/or stderr=PIPE 也。
注意
读取数据缓冲在内存中，所以不要使用此方法若数据尺寸很大 (或不受限制)。
发送信号 signal 到子级。
注意
在 Windows，SIGTERM 是别名化的 terminate() 。可以将 CTRL_C_EVENT 和 CTRL_BREAK_EVENT 发送给进程，启动时采用 creationflags 参数包括 CREATE_NEW_PROCESS_GROUP .
2.6 版新增。
Stop the child. On Posix OSs the method sends SIGTERM to the child. On Windows the Win32 API function TerminateProcess() 被调用以停止子级。
2.6 版新增。
Kills the child. On Posix OSs the function sends SIGKILL to the child. On Windows kill() 是别名化的 terminate() .
2.6 版新增。
下列属性也可用：
警告
使用 communicate() 而不是 .stdin.write , .stdout.read or .stderr.read 能避免由于任何其它 OS 管道缓冲填满和阻塞子级进程而导致死锁。
若 stdin 自变量为 PIPE , this attribute is a file object that provides input to the child process. Otherwise, it is None .
若 stdout 自变量为 PIPE , this attribute is a file object that provides output from the child process. Otherwise, it is None .
若 stderr 自变量为 PIPE , this attribute is a file object that provides error output from the child process. Otherwise, it is None .
子级进程的进程 ID。
注意：若设置 shell 自变量对于 True ，这是卵生 Shell 的进程 ID。
子级返回代码，设置通过 poll() and wait() (和间接通过 communicate() )。 None 值指示进程仍未终止。
负值 -N 指示子级被终止，通过信号 N (Unix only).
The STARTUPINFO 类和以下常量只可用于 Windows。
部分支持 Windows STARTUPINFO 结构用于 Popen creation.
A bit field that determines whether certain STARTUPINFO attributes are used when the process creates a window.
si = subprocess.STARTUPINFO() si.dwFlags = subprocess.STARTF_USESTDHANDLES | subprocess.STARTF_USESHOWWINDOW
若 dwFlags 指定 STARTF_USESTDHANDLES , this attribute is the standard input handle for the process. If STARTF_USESTDHANDLES is not specified, the default for standard input is the keyboard buffer.
若 dwFlags 指定 STARTF_USESTDHANDLES , this attribute is the standard output handle for the process. Otherwise, this attribute is ignored and the default for standard output is the console window’s buffer.
若 dwFlags 指定 STARTF_USESTDHANDLES , this attribute is the standard error handle for the process. Otherwise, this attribute is ignored and the default for standard error is the console window’s buffer.
若 dwFlags 指定 STARTF_USESHOWWINDOW , this attribute can be any of the values that can be specified in the nCmdShow parameter for the ShowWindow function, except for SW_SHOWDEFAULT . Otherwise, this attribute is ignored.
SW_HIDE is provided for this attribute. It is used when Popen is called with shell=True .
The subprocess 模块暴露以下常量。
The standard input device. Initially, this is the console input buffer, CONIN$ .
The standard output device. Initially, this is the active console screen buffer, CONOUT$ .
The standard error device. Initially, this is the active console screen buffer, CONOUT$ .
隐藏窗口。将激活另一窗口。
Specifies that the STARTUPINFO.hStdInput , STARTUPINFO.hStdOutput ，和 STARTUPINFO.hStdError attributes contain additional information.
Specifies that the STARTUPINFO.wShowWindow attribute contains additional information.
The new process has a new console, instead of inheriting its parent’s console (the default).
This flag is always set when Popen is created with shell=True .
A Popen creationflags parameter to specify that a new process group will be created. This flag is necessary for using os.kill() on the subprocess.
此标志会被忽略，若 CREATE_NEW_CONSOLE 被指定。
In this section, “a becomes b” means that b can be used as a replacement for a.
注意
All “a” functions in this section fail (more or less) silently if the executed program cannot be found; the “b” replacements raise OSError 代替。
In addition, the replacements using check_output() will fail with a CalledProcessError if the requested operation produces a non-zero return code. The output is still available as the output attribute of the raised exception.
In the following examples, we assume that the relevant functions have already been imported from the subprocess 模块。
output=`mycmd myarg` # becomes output = check_output(["mycmd", "myarg"])
output=`dmesg | grep hda` # becomes p1 = Popen(["dmesg"], stdout=PIPE) p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE) p1.stdout.close() # Allow p1 to receive a SIGPIPE if p2 exits. output = p2.communicate()[0]
The p1.stdout.close() call after starting the p2 is important in order for p1 to receive a SIGPIPE if p2 exits before p1.
Alternatively, for trusted input, the shell’s own pipeline support may still be used directly:
output=`dmesg | grep hda`
# becomes
output=check_output("dmesg | grep hda", shell=True)
status = os.system("mycmd" + " myarg") # becomes status = subprocess.call("mycmd" + " myarg", shell=True)
注意事项：
更现实范例看起来像这样：
try: retcode = call("mycmd" + " myarg", shell=True) if retcode < 0: print >>sys.stderr, "Child was terminated by signal", -retcode else: print >>sys.stderr, "Child returned", retcode except OSError as e: print >>sys.stderr, "Execution failed:", e
P_NOWAIT 范例：
pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg") ==> pid = Popen(["/bin/mycmd", "myarg"]).pid
P_WAIT 范例：
retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg") ==> retcode = call(["/bin/mycmd", "myarg"])
向量范例：
os.spawnvp(os.P_NOWAIT, path, args) ==> Popen([path] + args[1:])
环境范例：
os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
==>
Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})
pipe = os.popen("cmd", 'r', bufsize)
==>
pipe = Popen("cmd", shell=True, bufsize=bufsize, stdout=PIPE).stdout
pipe = os.popen("cmd", 'w', bufsize)
==>
pipe = Popen("cmd", shell=True, bufsize=bufsize, stdin=PIPE).stdin
(child_stdin, child_stdout) = os.popen2("cmd", mode, bufsize)
==>
p = Popen("cmd", shell=True, bufsize=bufsize,
stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdin, child_stdout) = (p.stdin, p.stdout)
(child_stdin,
child_stdout,
child_stderr) = os.popen3("cmd", mode, bufsize)
==>
p = Popen("cmd", shell=True, bufsize=bufsize,
stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True)
(child_stdin,
child_stdout,
child_stderr) = (p.stdin, p.stdout, p.stderr)
(child_stdin, child_stdout_and_stderr) = os.popen4("cmd", mode,
bufsize)
==>
p = Popen("cmd", shell=True, bufsize=bufsize,
stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True)
(child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout)
On Unix, os.popen2, os.popen3 and os.popen4 also accept a sequence as the command to execute, in which case arguments will be passed directly to the program without shell intervention. This usage can be replaced as follows:
(child_stdin, child_stdout) = os.popen2(["/bin/ls", "-l"], mode,
bufsize)
==>
p = Popen(["/bin/ls", "-l"], bufsize=bufsize, stdin=PIPE, stdout=PIPE)
(child_stdin, child_stdout) = (p.stdin, p.stdout)
返回代码处理翻译如下：
pipe = os.popen("cmd", 'w')
...
rc = pipe.close()
if rc is not None and rc >> 8:
print "There were some errors"
==>
process = Popen("cmd", 'w', shell=True, stdin=PIPE)
...
process.stdin.close()
if process.wait() != 0:
print "There were some errors"
(child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode)
==>
p = Popen("somestring", shell=True, bufsize=bufsize,
stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdout, child_stdin) = (p.stdout, p.stdin)
On Unix, popen2 also accepts a sequence as the command to execute, in which case arguments will be passed directly to the program without shell intervention. This usage can be replaced as follows:
(child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize,
mode)
==>
p = Popen(["mycmd", "myarg"], bufsize=bufsize,
stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdout, child_stdin) = (p.stdout, p.stdin)
popen2.Popen3 and popen2.Popen4 basically work as subprocess.Popen ，除了：
在 Windows， args sequence is converted to a string that can be parsed using the following rules (which correspond to the rules used by the MS C runtime):