import sys, os, stringdef vtkLoadPythonTkWidgets(interp):    """vtkLoadPythonTkWidgets(interp) -- load vtk-tk widget extensions    This is a mess of mixed python and tcl code that searches for the    shared object file that contains the python-vtk-tk widgets.  Both    the python path and the tcl path are searched.    """    name = 'vtkRenderingPythonTkWidgets'    pkgname = string.capitalize(string.lower(name))    # find out if the file is already loaded    loaded = interp.call('info', 'loaded')    if string.find(loaded, pkgname) >= 0:        return    # create the platform-dependent file name    prefix = ''    if os.name == 'posix':        prefix = 'lib'    extension = interp.call('info', 'sharedlibextension')    filename = prefix+name+extension    # create an extensive list of paths to search    pathlist = sys.path    # add tcl paths, ensure that {} is handled properly    try:        auto_paths = string.split(interp.getvar('auto_path'))    except AttributeError:        auto_paths = interp.getvar('auto_path')    for path in auto_paths:        prev = pathlist[-1]        try:                        # try block needed when one uses Gordon McMillan's Python            # Installer.            if len(prev) > 0 and prev[0] == '{' and prev[-1] != '}':                pathlist[-1] = prev+' '+path            else:                pathlist.append(path)        except AttributeError:            pass    # a common place for these sorts of things      if os.name == 'posix':        pathlist.append('/usr/local/lib')    # attempt to load    for path in pathlist:        try:            # try block needed when one uses Gordon McMillan's Python            # Installer.            if len(path) > 0 and path[0] == '{' and path[-1] == '}':                path = path[1:-1]            fullpath = os.path.join(path, filename)        except AttributeError:            pass        if ' ' in fullpath:            fullpath = '{'+fullpath+'}'        if interp.eval('catch {load '+fullpath+' '+pkgname+'}') == '0':            return    # re-generate the error    interp.call('load', filename)