urllib2.py 文件源码

def build_opener(*handlers):
    """Create an opener object from a list of handlers.

    The opener will use several default handlers, including support
    for HTTP, FTP and when applicable, HTTPS.

    If any of the handlers passed as arguments are subclasses of the
    default handlers, the default handlers will not be used.
    """
    import types
    def isclass(obj):
        return isinstance(obj, (types.ClassType, type))

    opener = OpenerDirector()
    default_classes = [ProxyHandler, UnknownHandler, HTTPHandler,
                       HTTPDefaultErrorHandler, HTTPRedirectHandler,
                       FTPHandler, FileHandler, HTTPErrorProcessor]
    if hasattr(httplib, 'HTTPS'):
        default_classes.append(HTTPSHandler)
    skip = set()
    for klass in default_classes:
        for check in handlers:
            if isclass(check):
                if issubclass(check, klass):
                    skip.add(klass)
            elif isinstance(check, klass):
                skip.add(klass)
    for klass in skip:
        default_classes.remove(klass)

    for klass in default_classes:
        opener.add_handler(klass())

    for h in handlers:
        if isclass(h):
            h = h()
        opener.add_handler(h)
    return opener