foo.py

class FakeSchemaHelper(object):
    def register_table(self, table):
        print "register_table(%s)" % table

    def register_columns(self, table, columns, read_only=None):
        print "register_column(%s, %s, %s)" % (table, str(columns),
                                               str(read_only))

    def register_all(self):
        print "register_all"


class SchemaHelperCommand(object):
    def __init__(self, method, *args, **kwargs):
        self.method = method
        self.args = args
        self.kwargs = kwargs

    def execute(self, helper):
        return self.method(helper, *self.args, **self.kwargs)


class Connection(object):
    def __init__(self):
        self.schema_filter = []

    def register_table(self, table, *args, **kwargs):
        self.schema_filter.append(
            SchemaHelperCommand(FakeSchemaHelper.register_table, table,
                                *args, **kwargs))

    def register_columns(self, table, columns, *args, **kwargs):
        self.schema_filter.append(
            SchemaHelperCommand(FakeSchemaHelper.register_columns, table,
                                columns, *args, **kwargs))

    def get_schema_helper(self):
        return FakeSchemaHelper()

    def update_schema_helper(self, helper):
        if not self.schema_filter:
            helper.register_all()
        else:
            for sfilter in self.schema_filter:
                sfilter.execute(helper)

    def start(self, table_name_list=None):
        """Start the OVSDB connection

        :param table_name_list: limit schema to these tables (deprecated)
        """

        helper = self.get_schema_helper()
        for table in table_name_list or []:
            self.register_table(table)
        self.update_schema_helper(helper)

if __name__ == '__main__':
    c = Connection()
    c.start()  # Should call register_all()
    c.register_table("Table1")
    c.register_columns("Table2", ['col1', 'col2', 'col3'])
    c.start()

I am not sure that using a Command object is clearer, but I don't have a lot of experience with the OVSDB native lib.

It doesn't have to be a lambda - it can be any callable that accepts the helper, e.g. a (client) function, or a class implementing call(self, helper).