Version 4.8

  • Returned behavior of searchwindowsize to that in 4.3 and earlier (searches are only done within the search window) (PR #579).
  • Fixed a bug truncating before attribute after a timeout (PR #579).
  • Fixed a bug where a search could be less than searchwindowsize if it was increased between calls (PR #579).
  • Minor test cleanups to improve portability (PR #580) (PR #581) (PR #582) (PR #583) (PR #584) (PR #585).
  • Disable chaining of timeout and EOF exceptions (PR #606).
  • Allow traceback included snippet length to be configured via str_last_chars rather than always 100 (PR #598).
  • Python 3 warning added to interact.py (PR #537).
  • Several doc updates.

Version 4.7

  • The pxssh.login() method now no longer requires a username if an ssh config is provided and will raise an error if neither are provided. (PR #562).
  • The pxssh.login() method now supports providing your own ssh command via the cmd parameter. (PR #528) (PR #563).
  • pxssh now supports the use_poll parameter which is passed into pexpect.spawn() (PR #542).
  • Minor bug fix with ssh_config. (PR #498).
  • replwrap.run_command() now has async support via an async_ parameter. (PR #501).
  • pexpect.spawn() will now read additional bytes if able up to a buffer limit. (PR #304).

Version 4.6

  • The pxssh.login() method now supports an ssh_config parameter, which can be used to specify a file path to an SSH config file (PR #490).
  • Improved compatibility for the crlf parameter of PopenSpawn (PR #493)
  • Fixed an issue in read timeout handling when using spawn and fdspawn with the use_poll parameter (PR #492).

Version 4.5

  • spawn and fdspawn now have a use_poll parameter. If this is True, they will use select.poll() instead of select.select(). poll() allows file descriptors above 1024, but it must be explicitly enabled due to compatibility concerns (PR #474).

  • The pxssh.login() method has several new and changed options:

    • The option password_regex allows changing the password prompt regex, for servers that include password: in a banner before reaching a prompt (PR #468).

    • login() now allows for setting up SSH tunnels to be requested once logged in to the remote server. This option is ssh_tunnels (PR #473). The structure should be like this:

        'local': ['2424:localhost:22'],   # Local SSH tunnels
        'remote': ['2525:localhost:22'],  # Remote SSH tunnels
        'dynamic': [8888],                # Dynamic/SOCKS tunnels
    • The option spawn_local_ssh=False allows subsequent logins from the remote session and treats the session as if it was local (PR #472).

    • Setting sync_original_prompt=False will prevent changing the prompt to something unique, in case the remote server is sensitive to new lines at login (PR #468).

    • If ssh_key=True is passed, the SSH client forces forwarding the authentication agent to the remote server instead of providing a key (PR #473).

Version 4.4

  • PopenSpawn now has a preexec_fn parameter, like spawn and subprocess.Popen, for a function to be called in the child process before executing the new command. Like in Popen, this works only in POSIX, and can cause issues if your application also uses threads (PR #460).
  • Significant performance improvements when processing large amounts of data (PR #464).
  • Ensure that spawn.closed gets set by close(), and improve an example for passing SIGWINCH through to a child process (PR #466).

Version 4.3.1

  • When launching bash for pexpect.replwrap, load the system bashrc from a couple of different common locations (PR #457), and then unset the PROMPT_COMMAND environment variable, which can interfere with the prompt we’re expecting (PR #459).

Version 4.3

  • The async= parameter to integrate with asyncio has become async_= (PR #431), as async is becoming a Python keyword from Python 3.6. Pexpect will still recognise async as an alternative spelling.
  • Similarly, the module pexpect.async became pexpect._async (PR #450). This module is not part of the public API.
  • Fix problems with asyncio objects closing file descriptors during garbage collection (#347, PR #376).
  • Set the .pid attribute of a PopenSpawn object (PR #417).
  • Fix passing Windows paths to PopenSpawn (PR #446).
  • PopenSpawn on Windows can pass string commands through to Popen without splitting them into a list (PR #447).
  • Stop shlex trying to read from stdin when PopenSpawn is passed cmd=None (#433, PR #434).
  • Ensure that an error closing a Pexpect spawn object raises a Pexpect error, rather than a Ptyprocess error (#383, PR #386).
  • Cleaned up invalid backslash escape sequences in strings (PR #430, PR #445).
  • The pattern for a password prompt in pexpect.pxssh changed from password to password: (PR #452).
  • Correct docstring for using unicode with spawn (PR #395).
  • Various other improvements to documentation.

Version 4.2.1

  • Fix to allow running env in replwrap-ed bash.
  • Raise more informative exception from pxssh if it fails to connect.
  • Change passmass example to not log passwords entered.

Version 4.2

  • Change: When an env parameter is specified to the spawn or run family of calls containing a value for PATH, its value is used to discover the target executable from a relative path, rather than the current process’s environment PATH. This mirrors the behavior of subprocess.Popen() in the standard library (#348).
  • Regression: Re-introduce capability for read_nonblocking() in class fdspawn as previously supported in version 3.3 (#359).

Version 4.0

  • Integration with asyncio: passing async=True to expect(), expect_exact() or expect_list() will make them return a coroutine. You can get the result using yield from, or wrap it in an asyncio.Task. This allows the event loop to do other things while waiting for output that matches a pattern.
  • Experimental support for Windows (with some caveats)—see Pexpect on Windows.
  • Enhancement: allow method as callbacks of argument events for pexpect.run() (#176).
  • It is now possible to call wait() multiple times, or after a process is already determined to be terminated without raising an exception (PR #211).
  • New pexpect.spawn keyword argument, dimensions=(rows, columns) allows setting terminal screen dimensions before launching a program (#122).
  • Fix regression that prevented executable, but unreadable files from being found when not specified by absolute path – such as /usr/bin/sudo (#104).
  • Fixed regression when executing pexpect with some prior releases of the multiprocessing module where stdin has been closed (#86).

Backwards incompatible changes

  • Deprecated pexpect.screen and pexpect.ANSI. Please use other packages such as pyte to emulate a terminal.
  • Removed the independent top-level modules (pxssh fdpexpect FSM screen ANSI) which were installed alongside Pexpect. These were moved into the Pexpect package in 3.0, but the old names were left as aliases.
  • Child processes created by Pexpect no longer ignore SIGHUP by default: the ignore_sighup parameter of pexpect.spawn defaults to False. To get the old behaviour, pass ignore_sighup=True.

Version 3.3

  • Added a mechanism to wrap REPLs, or shells, in an object which can conveniently be used to send commands and wait for the output (pexpect.replwrap).
  • Fixed issue where pexpect would attempt to execute a directory because it has the ‘execute’ bit set (#37).
  • Removed the pexpect.psh module. This was never documented, and we found no evidence that people use it. The new pexpect.replwrap module provides a more flexible alternative.
  • Fixed TypeError: got <type 'str'> ('\r\n') as pattern in spawnu.readline() method (#67).
  • Fixed issue where EOF was not correctly detected in interact(), causing a repeating loop of output on Linux, and blocking before EOF on BSD and Solaris (#49).
  • Several Solaris (SmartOS) bugfixes, preventing IOError exceptions, especially when used with cron(1) (#44).
  • Added new keyword argument echo=True for spawn. On SVR4-like systems, the method isatty() will always return False: the child pty does not appear as a terminal. Therefore, setecho(), getwinsize(), setwinsize(), and waitnoecho() are not supported on those platforms.

After this, we intend to start working on a bigger refactoring of the code, to be released as Pexpect 4. There may be more bugfix 3.x releases, however.

Version 3.2

  • Fix exception handling from select.select() on Python 2 (PR #38). This was accidentally broken in the previous release when it was fixed for Python 3.
  • Removed a workaround for TIOCSWINSZ on very old systems, which was causing issues on some BSD systems (PR #40).
  • Fixed an issue with exception handling in pxssh (PR #43)

The documentation for pxssh was improved.

Version 3.1

  • Fix an issue that prevented importing pexpect on Python 3 when sys.stdout was reassigned (#30).
  • Improve prompt synchronisation in pxssh (PR #28).
  • Fix pickling exception instances (PR #34).
  • Fix handling exceptions from select.select() on Python 3 (PR #33).

The examples have also been cleaned up somewhat - this will continue in future releases.

Version 3.0

The new major version number doesn’t indicate any deliberate API incompatibility. We have endeavoured to avoid breaking existing APIs. However, pexpect is under new maintenance after a long dormancy, so some caution is warranted.

  • A new unicode API was introduced.
  • Python 3 is now supported, using a single codebase.
  • Pexpect now requires at least Python 2.6 or 3.2.
  • The modules other than pexpect, such as pexpect.fdpexpect and pexpect.pxssh, were moved into the pexpect package. For now, wrapper modules are installed to the old locations for backwards compatibility (e.g. import pxssh will still work), but these will be removed at some point in the future.
  • Ignoring SIGHUP is now optional - thanks to Kimmo Parviainen-Jalanko for the patch.

We also now have docs on ReadTheDocs, and continuous integration on Travis CI.

Version 2.4

  • Fix a bug regarding making the pty the controlling terminal when the process spawning it is not, actually, a terminal (such as from cron)

Version 2.3

  • Fixed OSError exception when a pexpect object is cleaned up. Previously, you might have seen this exception:

    Exception exceptions.OSError: (10, 'No child processes')
    in <bound method spawn.__del__ of <pexpect.spawn instance at 0xd248c>> ignored

    You should not see that anymore. Thanks to Michael Surette.

  • Added support for buffering reads. This greatly improves speed when trying to match long output from a child process. When you create an instance of the spawn object you can then set a buffer size. For now you MUST do the following to turn on buffering – it may be on by default in future version:

    child = pexpect.spawn ('my_command')
    child.maxread=1000 # Sets buffer to 1000 characters.
  • I made a subtle change to the way TIMEOUT and EOF exceptions behave. Previously you could either expect these states in which case pexpect will not raise an exception, or you could just let pexpect raise an exception when these states were encountered. If you expected the states then the before property was set to everything before the state was encountered, but if you let pexpect raise the exception then before was not set. Now, the before property will get set either way you choose to handle these states.

  • The spawn object now provides iterators for a file-like interface. This makes Pexpect a more complete file-like object. You can now write code like this:

    child = pexpect.spawn ('ls -l')
    for line in child:
        print line
  • write and writelines() no longer return a value. Use send() if you need that functionality. I did this to make the Spawn object more closely match a file-like object.

  • Added the attribute exitstatus. This will give the exit code returned by the child process. This will be set to None while the child is still alive. When isalive() returns 0 then exitstatus will be set.

  • Made a few more tweaks to isalive() so that it will operate more consistently on different platforms. Solaris is the most difficult to support.

  • You can now put TIMEOUT in a list of expected patterns. This is just like putting EOF in the pattern list. Expecting for a TIMEOUT may not be used as often as EOF, but this makes Pexpect more consistent.

  • Thanks to a suggestion and sample code from Chad J. Schroeder I added the ability for Pexpect to operate on a file descriptor that is already open. This means that Pexpect can be used to control streams such as those from serial port devices. Now, you just pass the integer file descriptor as the “command” when constructing a spawn open. For example on a Linux box with a modem on ttyS1:

    fd = os.open("/dev/ttyS1", os.O_RDWR|os.O_NONBLOCK|os.O_NOCTTY)
    m = pexpect.spawn(fd) # Note integer fd is used instead of usual string.
    m.send("+++") # Escape sequence
    m.send("ATZ0\r") # Reset modem to profile 0
    rval = m.expect(["OK", "ERROR"])
  • read() was renamed to read_nonblocking(). Added new read() method that matches file-like object interface. In general, you should not notice the difference except that read() no longer allows you to directly set the timeout value. I hope this will not effect any existing code. Switching to read_nonblocking() should fix existing code.

  • Changed the name of set_echo() to setecho().

  • Changed the name of send_eof() to sendeof().

  • Modified kill() so that it checks to make sure the pid isalive().

  • modified spawn() (really called from __spawn()) so that it does not raise an exception if setwinsize() fails. Some platforms such as Cygwin do not like setwinsize. This was a constant problem and since it is not a critical feature I decided to just silence the error. Normally I don’t like to do that, but in this case I’m making an exception.

  • Added a method close() that does what you think. It closes the file descriptor of the child application. It makes no attempt to actually kill the child or wait for its status.

  • Add variables __version__ and __revision__ (from cvs) to the pexpect modules. This is mainly helpful to me so that I can make sure that I’m testing with the right version instead of one already installed.

  • log_open() and log_close( have been removed. Now use setlog(). The setlog() method takes a file object. This is far more flexible than the previous log method. Each time data is written to the file object it will be flushed. To turn logging off simply call setlog() with None.

  • renamed the isAlive() method to isalive() to match the more typical naming style in Python. Also the technique used to detect child process status has been drastically modified. Previously I did some funky stuff with signals which caused indigestion in other Python modules on some platforms. It was a big headache. It still is, but I think it works better now.

  • attribute matched renamed to after

  • new attribute match

  • The expect_eof() method is gone. You can now simply use the expect() method to look for EOF.

  • Pexpect works on OS X, but the nature of the quirks cause many of the tests to fail. See bugs. (Incomplete Child Output). The problem is more than minor, but Pexpect is still more than useful for most tasks.

  • Solaris: For some reason, the second time a pty file descriptor is created and deleted it never gets returned for use. It does not effect the first time or the third time or any time after that. It’s only the second time. This is weird… This could be a file descriptor leak, or it could be some peculiarity of how Solaris recycles them. I thought it was a UNIX requirement for the OS to give you the lowest available filedescriptor number. In any case, this should not be a problem unless you create hundreds of pexpect instances… It may also be a pty module bug.

Moves and forks

  • Pexpect development used to be hosted on Sourceforge.
  • In 2011, Thomas Kluyver forked pexpect as ‘pexpect-u’, to support Python 3. He later decided he had taken the wrong approach with this.
  • In 2012, Noah Spurrier, the original author of Pexpect, moved the project to Github, but was still too busy to develop it much.
  • In 2013, Thomas Kluyver and Jeff Quast forked Pexpect again, intending to call the new fork Pexpected. Noah Spurrier agreed to let them use the name Pexpect, so Pexpect versions 3 and above are based on this fork, which now lives here on Github.