Speech recognition in Windows using Python

Why use Python?

I wrote this code after being frustrated by several VB and C voice recognition programs. None of them allowed any significant user scripting; whereas a system written in Python is very easy to extend using Python’s “exec” command.

Installing the Microsoft Speech SDK

The Microsoft Speech SDK is a free download from http://microsoft.com/speech/.

After installing it, use the MakePy utility to produce a Python stub for the COM object (in PythonWin, select Tools | COM MakePy utility | Microsoft Speech Object Library 5.1).

Simple voice recognition

This is an example of using the MS Speech SDK for simple command and control speech recognition. I’ve submitted it to the Python Cookbook.

from win32com.client import constants
import win32com.client
import pythoncom

*"""Sample code for using the Microsoft Speech SDK 5.1 via COM in Python.
    Requires that the SDK be installed (it's a free download from
    and that MakePy has been used on it (in PythonWin,
    select Tools | COM MakePy Utility | Microsoft Speech Object Library 5.1).

    After running this, then saying "One", "Two", "Three" or "Four" should
    display "You said One" etc on the console. The recognition can be a bit
    shaky at first until you've trained it (via the Speech entry in the Windows
    Control Panel."""*
class SpeechRecognition:
    *""" Initialize the speech recognition with the passed in list of words """*
    def __init__(self, wordsToAdd):
        *# For text-to-speech*
        self.speaker = win32com.client.Dispatch("SAPI.SpVoice")
        *# For speech recognition - first create a listener*
        self.listener = win32com.client.Dispatch("SAPI.SpSharedRecognizer")
        *# Then a recognition context*
        self.context = self.listener.CreateRecoContext()
        *# which has an associated grammar*
        self.grammar = self.context.CreateGrammar()
        *# Do not allow free word recognition - only command and control*
            *# recognizing the words in the grammar only*
        *# Create a new rule for the grammar, that is top level (so it begins*
            *# a recognition) and dynamic (ie we can change it at runtime)*
        self.wordsRule = self.grammar.Rules.Add("wordsRule",
                        constants.SRATopLevel + constants.SRADynamic, 0)
        *# Clear the rule (not necessary first time, but if we're changing it*
            *# dynamically then it's useful)*
        *# And go through the list of words, adding each to the rule*
        [ self.wordsRule.InitialState.AddWordTransition(None, word) for word in wordsToAdd ]
        *# Set the wordsRule to be active*
        self.grammar.CmdSetRuleState("wordsRule", 1)
        *# Commit the changes to the grammar*
        *# And add an event handler that's called back when recognition occurs*
        self.eventHandler = ContextEvents(self.context)
        *# Announce we've started*
        self.say("Started successfully")
    *"""Speak a word or phrase"""*
    def say(self, phrase):

*"""The callback class that handles the events raised by the speech object.
    See "Automation | SpSharedRecoContext (Events)" in the MS Speech SDK
    online help for documentation of the other events supported. """*
class ContextEvents(win32com.client.getevents("SAPI.SpSharedRecoContext")):
    *"""Called when a word/phrase is successfully recognized  -
        ie it is found in a currently open grammar with a sufficiently high
    def OnRecognition(self, StreamNumber, StreamPosition, RecognitionType, Result):
        newResult = win32com.client.Dispatch(Result)
        print "You said: ",newResult.PhraseInfo.GetText()
if __name__=='__main__':
    wordsToAdd = [ "One", "Two", "Three", "Four" ]
    speechReco = SpeechRecognition(wordsToAdd)
    while 1:

Download this

A more useful Windows speech recognition application

The code above is interesting as an example of how to use the speech SDK, but it’s not that useful in its own right. The following code implements a simple MS Windows application that has a listbox containing recognized words, and an associated fragment of Python to execute for each one. The user interface is crude but effective.

I have found it most useful to use it with the “start” method, to launch arbitrary windows executables (I have “Prompt” mapped to start("cmd"), the “browseTo” method (for example, I have “Google” mapped to the macro browseTo("http://www.google.com/")) and the sendKeys method (I have “Close this” mapped to sendKeys("%{F4}")).

The code requires that the MS Speech SDK be installed and that MakePy has been run against it, as described above. It also requires the wxPython libraries have been installed.

It is licenced under the GNU General Public License (GPL).

Download the code