Python Flask：TypeError: unsupported operand type(s) for -: ‘str‘ and ‘int‘

背景

项目中常见的分页功能，代码如下：

# 收藏列表
@blog_base_blueprint.route('/resource_like_list/<int:user_id>', methods=['POST'])
def getResourceLikeList(user_id):

    page_size = request.form.get('page_size', default=2)

    page_num = request.form.get('page_num', default=1)

    offset = (page_num - 1) * page_size

    print(offset)
    print(page_num)
    print(page_size)

    logs = models.ResourceLikeLog.query.filter_by(user_id=user_id).filter_by(delete_flag=0).order_by(models.ResourceLikeLog.id.desc()).offset(
        offset).limit(page_size)

    return jsonify({
        'code': 1,
        'msg': '成功',
        'data': [log.to_format() for log in logs]
    })

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项目启动时可以使用，但是我在postman中传了page_num的参数，然后就报异常TypeError: unsupported operand type(s) for -: 'str' and 'int';
根据异常信息，是类型的的问题，需要将str转为int，这里还是很好处理的，在接受参数的时候，处理一下就可以喽。

request.form.get（）

点到源码，

    def get(self, key, default=None, type=None):
        """Return the default value if the requested data doesn't exist.
        If `type` is provided and is a callable it should convert the value,
        return it or raise a :exc:`ValueError` if that is not possible.  In
        this case the function will return the default as if the value was not

        :param key: The key to be looked up.
        :param default: The default value to be returned if the key can't
                        be looked up.  If not further specified `None` is
                        returned.
        :param type: A callable that is used to cast the value in the
                     :class:`MultiDict`.  If a :exc:`ValueError` is raised
                     by this callable the default value is returned.
        """
        try:
            rv = self[key]
        except KeyError:
            return default
        if type is not None:
            try:
                rv = type(rv)
            except ValueError:
                rv = default
        return rv
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能看到这个方法的参数：有默认值，还有一个参数类型的参数，用来强制转换参数类型，调整代码为:

    page_size = request.form.get('page_size', default=2, type=int)

    page_num = request.form.get('page_num', default=1, type=int)
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