objects.py 文件源码

def __getitem__(self, i):
        if isinstance(i, slice):
            start = i.start or 0
            stop = i.stop

            db = self.db
            if start < 0:
                pos0 = '(%s - %d)' % (self.len(), abs(start) - 1)
            else:
                pos0 = start + 1

            maxint = sys.maxint if PY2 else sys.maxsize
            if stop is None or stop == maxint:
                length = self.len()
            elif stop < 0:
                length = '(%s - %d - %s)' % (self.len(), abs(stop) - 1, pos0)
            else:
                length = '(%s - %s)' % (stop + 1, pos0)

            return Expression(db, self._dialect.substring,
                              self, (pos0, length), self.type)
        else:
            return self[i:i + 1]