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problem with implenting __len__ with sqlalchemy func. 计算出某种再入侵错误
原标题:problem with implenting __len__ with sqlalchemy func.count getting some kind of recursion error

该法典应包含以下文字:

    def __len__(self):

    from sqlalchemy import func
    self.len = session.query(func.count(Question.id)).scalar()
    return int(self.len)

def __repr__(self):

    self.repr = "traffic theory question, current number of questions:{0}".format(self.__len__)
    return self.repr

我得到的东西(三个上层一线不断重复,然后按以下线终止):

  File "C:Python27dirfile.py", line 129, in __repr__
    self.repr = "traffic theory question, current number of questions:{0}".format(self.__len__)
RuntimeError: maximum recursion depth exceeded while getting the str of an object

我应强调,只有打电话<>repr时,我才会发现这一错误。 班级方法,但当我叫Llen(q)时(q)是同我一起工作的一米级单位)我得到正确答案!

任何 c?

最佳回答

页: 1

When you try to format(self.__len__), it calls repr on the instance referred to by self, creating the recursion.

您需要使用<代码>format,. 自行.__len__(<>/code>(或len(其本国).len

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