wexpect 3.3.2

Windows alternative of pexpect

wexpect

Wexpect is a Windows variant of pexpect.

Pexpect is a Python module for spawning child applications and controlling them automatically.

You need wexpect if...

• you want to control any windows console application from python script.
• you want to write test-automation script for a windows console application.
• you want to automate your job by controlling multiple application parallel, synchoronusly.

Install

pip install wexpect

Usage

To interract with a child process use spawn method:

import wexpect 
child = wexpect.spawn('cmd.exe')
child.expect('>')
child.sendline('ls')
child.expect('>')
print(child.before)
child.sendline('exit')

For more information see examples folder.

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REFACTOR

The original wexpect has some structural weakness, which leads me to rewrite the whole code. The first variant of the new structure is delivered with v3.2.0. Note, that the default is the old variant (legacy_wexpect), to use the new you need to set the WEXPECT_SPAWN_CLASS environment variable to SpawnPipe or SpawnSocket, which are the two new structured spawn class.

Old vs new

But what is the difference between the old and new and what was the problem with the old?

Generally, wexpect (both old and new) has three processes:

• host is our original pyton script/program, which want to launch the child.
• console is a process which started by the host, and launches the child. (This is a python script)
• child is the process which want to be launced.

The child and the console has a common Windows console, distict from the host.

The legacy_wexpect's console is a thin script, almost do nothing. It initializes the Windows's console, and monitors the host and child processes. The magic is done by the host process, which has the switchTo() and switchBack() functions, which (de-) attaches the child-console Windows-console. The host manipulates the child's console directly. This direct manipuation is the structural weakness. The following task/usecases are hard/impossibile:

• thread-safe multiprocessing of the host.
• logging (both console and host)
• using in grapichal IDE or with pytest
• This variant is highly depends on the pywin32 package.

The new structure's console is a thik script. The console process do the major console manipulation, which is controlled by the host via socket (see SpawnSocket) or named-pipe (SpawnPipe). The host only process the except-loops.

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What is it?

Wexpect is a Python module for spawning child applications and controlling them automatically. Wexpect can be used for automating interactive applications such as ssh, ftp, passwd, telnet, etc. It can be used to a automate setup scripts for duplicating software package installations on different servers. It can be used for automated software testing. Wexpect is in the spirit of Don Libes' Expect, but Wexpect is pure Python. Other Expect-like modules for Python require TCL and Expect or require C extensions to be compiled. Wexpect does not use C, Expect, or TCL extensions.

Original Pexpect should work on any platform that supports the standard Python pty module. While Wexpect works on Windows platforms. The Wexpect interface focuses on ease of use so that simple tasks are easy.

History

Wexpect is a one-file code developed at University of Washington. There are several copy and reference to this code with very few (almost none) documentation nor integration.

This repo tries to fix these limitations, with a few example code and pypi integration.

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Dev

Thanks for any contributing!

Test

To run test, enter into the folder of the wexpect's repo then:

python -m unittest

Deploy

The deployment itself is automated and done by appveyor. See after_test section in appveyor.yml for more details.

The wexpect uses pbr for managing releasing procedures. The versioning is handled by the pbr. The "master-version" is the git tag. Pbr derives the package version from the git tags.

Basic behaviour

Let's go through the example code:

import wexpect 
child = wexpect.spawn('cmd.exe')
child.expect('>')
child.sendline('ls')
child.expect('>')
print(child.before)
child.sendline('exit')

spawn()

child = wexpect.spawn('cmd.exe')

Call trace:

• ::spawn
• spawn_windows::init()
• spawn_windows::_spawn()
• Wtty::spawn()
• Wtty::startChild()
• win32process.CreateProcess()

expect()

child.expect('>')

Call trace:

• spawn_windows::expect()
• spawn_windows::expect_list()
• spawn_windows::expect_loop()
• spawn_windows::read_nonblocking()
• Wtty::read_nonblocking()
• Wtty::readConsoleToCursor()
• Wtty::readConsole()
• __consout.ReadConsoleOutputCharacter()

sendline()

child.sendline('ls')

• spawn_windows::sendline()
• spawn_windows::send()
• Wtty::write()