Python pip 模块，backwardcompat() 实例源码

def connect(self):

        self.connection_kwargs = {}

        #TODO: refactor compatibility logic into backwardcompat?

        # for > py2.5
        if hasattr(self, 'timeout'):
            self.connection_kwargs.update(timeout = self.timeout)

        # for >= py2.7
        if hasattr(self, 'source_address'):
            self.connection_kwargs.update(source_address = self.source_address)

        sock = socket.create_connection((self.host, self.port), **self.connection_kwargs)

        # for >= py2.7
        if getattr(self, '_tunnel_host', None):
            self.sock = sock
            self._tunnel()

        # get alternate bundle or use our included bundle
        cert_path = os.environ.get('PIP_CERT', '') or default_cert_path

        self.sock = ssl.wrap_socket(sock,
                                self.key_file,
                                self.cert_file,
                                cert_reqs=ssl.CERT_REQUIRED,
                                ca_certs=cert_path)

        try:
            match_hostname(self.sock.getpeercert(), self.host)
        except CertificateError:
            self.sock.shutdown(socket.SHUT_RDWR)
            self.sock.close()
            raise