It is safe to catch this exception and retry the wait. Use Popen. The function is implemented using a busy loop non-blocking call and short sleeps. Use the asyncio module for an asynchronous wait: see asyncio. Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate and set the returncode attribute. The optional input argument should be data to be sent to the child process, or None , if no data should be sent to the child.
If streams were opened in text mode, input must be a string. Otherwise, it must be bytes. The data will be strings if streams were opened in text mode; otherwise, bytes. If the process does not terminate after timeout seconds, a TimeoutExpired exception will be raised.
Catching this exception and retrying communication will not lose any output. The child process is not killed if the timeout expires, so in order to cleanup properly a well-behaved application should kill the child process and finish communication:. The data read is buffered in memory, so do not use this method if the data size is large or unlimited. Stop the child. Kills the child. On Windows kill is an alias for terminate.
The args argument as it was passed to Popen — a sequence of program arguments or else a single string. If the stdin argument was PIPE , this attribute is a writeable stream object as returned by open.
If the stdout argument was PIPE , this attribute is a readable stream object as returned by open. Reading from the stream provides output from the child process. If the stderr argument was PIPE , this attribute is a readable stream object as returned by open.
Reading from the stream provides error output from the child process. Use communicate rather than. Note that if you set the shell argument to True , this is the process ID of the spawned shell.
The child return code, set by poll and wait and indirectly by communicate. The following attributes can be set by passing them as keyword-only arguments. Otherwise, this attribute is ignored. The handles must be temporarily made inheritable by os. In a multithreaded process, use caution to avoid leaking handles that are marked inheritable when combining this feature with concurrent calls to other process creation functions that inherit all handles such as os.
This also applies to standard handle redirection, which temporarily creates inheritable handles. The subprocess module exposes the following constants. The standard input device. The standard output device. The standard error device. A Popen creationflags parameter to specify that a new process group will be created.
This flag is necessary for using os. A Popen creationflags parameter to specify that a new process will have an above average priority.
A Popen creationflags parameter to specify that a new process will have a below average priority. A Popen creationflags parameter to specify that a new process will have a high priority.
A Popen creationflags parameter to specify that a new process will have an idle lowest priority. A Popen creationflags parameter to specify that a new process will have an normal priority. A Popen creationflags parameter to specify that a new process will have realtime priority. A Popen creationflags parameter to specify that a new process will not create a window. A Popen creationflags parameter to specify that a new process does not inherit the error mode of the calling process. Instead, the new process gets the default error mode.
This feature is particularly useful for multithreaded shell applications that run with hard errors disabled. A Popen creationflags parameter to specify that a new process is not associated with the job.
Prior to Python 3. You can now use run in many cases, but lots of existing code calls these functions. Wait for command to complete, then return the returncode attribute.
Code needing to capture stdout or stderr should use run instead:. The arguments shown above are merely some common ones. The full function signature is the same as that of the Popen constructor - this function passes all supplied arguments other than timeout directly through to that interface.
The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from. Run command with arguments. Wait for command to complete. If the return code was zero then return, otherwise raise CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute. If the return code was non-zero it raises a CalledProcessError. The CalledProcessError object will have the return code in the returncode attribute and any output in the output attribute.
The full function signature is largely the same as that of run - most arguments are passed directly through to that interface. By default, this function will return the data as encoded bytes. The actual encoding of the output data may depend on the command being invoked, so the decoding to text will often need to be handled at the application level.
See run for details. 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 module. The p1. The call return value is encoded differently to that of os. The os. If it is a list, the command is directly executed. Popen3 and popen2. Popen4 basically work as subprocess.
Popen , except that:. Popen raises an exception if the execution fails. This module also provides the following legacy functions from the 2. These operations implicitly invoke the system shell and none of the guarantees described above regarding security and exception handling consistency are valid for these functions.
Return exitcode, output of executing cmd in a shell. Execute the string cmd in a shell with Popen. The locale encoding is used; see the notes on Frequently Used Arguments for more details. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
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