def addsitepackages(known_paths):
    """Add site-packages (and possibly site-python) to sys.path"""
    sitedirs = []
    seen = []

    for prefix in PREFIXES:
        if not prefix or prefix in seen:
            continue
        seen.append(prefix)

        if sys.platform in ('os2emx', 'riscos'):
            sitedirs.append(os.path.join(prefix, "Lib", "site-packages"))
        elif os.sep == '/':
            sitedirs.append(os.path.join(prefix, "local/lib",
                                        "python" + sys.version[:3],
                                        "dist-packages"))
            sitedirs.append(os.path.join(prefix, "lib",
                                        "python" + sys.version[:3],
                                        "dist-packages"))
            sitedirs.append(os.path.join(prefix, "lib", "dist-python"))

            ##################
        # added following line to make site-packages part of default search path
            #################
            sitedirs.append(os.path.join(prefix, "lib",
                                        "python" + sys.version[:3],
                                        "site-packages"))

        else:
            sitedirs.append(prefix)
            sitedirs.append(os.path.join(prefix, "lib", "site-packages"))

        if sys.platform == "darwin":
            # for framework builds *only* we add the standard Apple
            # locations. Currently only per-user, but /Library and
            # /Network/Library could be added too
            if 'Python.framework' in prefix:
                sitedirs.append(
                    os.path.expanduser(
                        os.path.join("~", "Library", "Python",
                                     sys.version[:3], "site-packages")))

    for sitedir in sitedirs:
        if os.path.isdir(sitedir):
            addsitedir(sitedir, known_paths)

    return known_paths