如果值无效，flask+marshmallow 设置默认值答案

【问题标题】：flask+marshmallow set default value if value is invalid如果值无效，flask+marshmallow 设置默认值
【发布时间】：2019-09-18 12:44:03
【问题描述】：

我正在使用 flask+marshmallow 来验证用户有效负载。当收到任何 GET/POST 请求时，我将处理 request.args 或 request.form 到 request.req_data。下面是代码。

class BaseMethodView(MethodView):

    view_template = None


    def __init__(self, *args, **kwargs):
        assert issubclass(self.validator_class, core_validator.BaseValidator), (
            "Invalid validator found."
        )
        assert issubclass(self.service_class, BaseService), "Invalid Service found."
        assert self.view_template, "Template not defined"
        super().__init__(*args, **kwargs)

    def validate(self, payload, *args, **kwargs):
        self.validator_class().validate(payload)

    def process_request(self):
        search_data = self.service_class(request).execute()
        return render_template(self.view_template, data=search_data)

    def get(self):
        request.req_data = request.args.copy()
        self.validate(request.req_data)
        return self.process_request()

    def post(self):
        request.req_data = request.form.copy()
        self.validate(request.req_data)
        return self.process_request()

要求-在验证器中，我正在验证字段。如果某些字段值无效，那么我想设置为默认值而不是引发任何异常。怎么办？

class CategoryField(fields.String):
    def _deserialize(self, value, attr, data, **kwargs):
        if value not in ("choice1", "choice2", "choice3"):
            return "choice1"
        super()._deserialize(value, attr, data)


class SearchValidator(core_validator.BaseValidator):
    query = fields.Str(required=True)
    cat = CategoryField()

    class Meta:
        strict = True
        skip_on_field_errors=False
        # INCLUDE: pass those keys/values as is, with no validation performed
        unknown = INCLUDE

如果不是棉花糖，那么你能推荐一些其他更好的图书馆吗？我也在尝试marshmallow.decorators.post_dump，但没有运气。

【问题讨论】：

标签： python python-3.x flask marshmallow

【解决方案1】：

您必须调用Schema().validate() 方法。而是调用Schema().load(request.args) 方法，该方法总是调用用@post_load 装饰的方法。也不要忘记在 Metas 类模式中设置postprocess = True。

class SearchValidator(core_validator.BaseValidator):
    query = fields.Str(required=True)
    cat = CategoryField()

    class Meta:
        strict = True
        skip_on_field_errors=False
        # INCLUDE: pass those keys/values as is, with no validation performed
        unknown = INCLUDE
        postprocess = True

调用时，使用SearchValidator().load(payload) 而不是SearchValidator().validate()。

【讨论】：