This script to adds Python to the Windows search path (environment path). It modifies the current user (HKCU) tree of the registry.

"""Add Python to the search path on Windows

This is a simple script to add Python to the Windows search path. It
modifies the current user (HKCU) tree of the registry.

Copyright (c) 2008 by Christian Heimes <christian@cheimes.de>
Licensed to PSF under a Contributor Agreement.
"""

import _winreg
import os
import site
import sys

HKCU = _winreg.HKEY_CURRENT_USER
ENV = "Environment"
PATH = "PATH"
DEFAULT = u"%PATH%"


def modify():
    pythonpath = os.path.dirname(os.path.normpath(sys.executable))
    scripts = os.path.join(pythonpath, "Scripts")
    appdata = os.environ["APPDATA"]
    if hasattr(site, "USER_SITE"):
        userpath = site.USER_SITE.replace(appdata, "%APPDATA%")
        userscripts = os.path.join(userpath, "Scripts")
    else:
        userscripts = None

    with _winreg.CreateKey(HKCU, ENV) as key:
        try:
            envpath = _winreg.QueryValueEx(key, PATH)[0]
        except WindowsError:
            envpath = DEFAULT

        paths = [envpath]
        for path in (pythonpath, scripts, userscripts):
            if path and path not in envpath and os.path.isdir(path):
                paths.append(path)

        envpath = os.pathsep.join(paths)
        _winreg.SetValueEx(key, PATH, 0, _winreg.REG_EXPAND_SZ, envpath)
        return paths, envpath


def main():
    paths, envpath = modify()
    if len(paths) > 1:
        print "Path(s) added:"
        print '\n'.join(paths[1:])
    else:
        print "No path was added"
    print "\nPATH is now:\n%s\n" % envpath
    print "Expanded:"
    print _winreg.ExpandEnvironmentStrings(envpath)

if __name__ == '__main__':
    main()