Python调用父类方法时为何需传入两个参数？

Hey there! Let's figure out how to call the cleanse method from ParentSerializer in your ChildSerializer. Looking at your code, there are a couple of adjustments needed to make this work properly. Below are two practical solutions based on your use case:

方案1：让ChildSerializer继承ParentSerializer #

If your ChildSerializer doesn't need to stick strictly to inheriting GenericSerializer, the simplest approach is to have it inherit from ParentSerializer directly. This lets you call the parent's cleanse method naturally via the instance itself:

from rest_framework.serializers import ModelSerializer, GenericSerializer

class ParentSerializer(ModelSerializer):
    def cleanse(self):
        if hasattr(self, 'initial_data'):
            val1 = self.initial_data['name']
            val2 = self.initial_data['age']
            val3 = self.initial_data['city']
            # You can modify the initial_data here if needed
            return self.initial_data

class ChildSerializer(ParentSerializer):  # Switch inheritance to ParentSerializer
    def is_valid(self, raise_exception=False):
        if hasattr(self, 'initial_data'):
            # Call the parent's cleanse method directly
            cleaned_data = self.cleanse()
            # Update initial_data with cleaned results if required
            self.initial_data = cleaned_data
        
        # Continue with the default validation logic
        return super().is_valid(raise_exception=raise_exception)

方案2：实例化ParentSerializer（保留GenericSerializer继承） #

If ChildSerializer must inherit GenericSerializer, you can create an instance of ParentSerializer with your current data and context, then call its cleanse method:

from rest_framework.serializers import ModelSerializer, GenericSerializer

class ParentSerializer(ModelSerializer):
    def cleanse(self):
        if hasattr(self, 'initial_data'):
            val1 = self.initial_data['name']
            val2 = self.initial_data['age']
            val3 = self.initial_data['city']
            return self.initial_data

class ChildSerializer(GenericSerializer):
    def is_valid(self, raise_exception=False):
        if hasattr(self, 'initial_data'):
            # Initialize ParentSerializer with current data and context
            parent_serializer = ParentSerializer(
                data=self.initial_data,
                context=self.context  # Pass context to maintain request/other info
            )
            # Call the cleanse method
            cleaned_data = parent_serializer.cleanse()
            # Update initial_data for subsequent validation
            self.initial_data = cleaned_data
        
        # Proceed with default validation
        return super().is_valid(raise_exception=raise_exception)

Key Notes #

• The inheritance approach is better if you want to reuse all of ParentSerializer's fields and logic in ChildSerializer.
• When instantiating ParentSerializer, always pass the context parameter — this ensures the parent serializer has access to critical data like the request object if needed.
• If your cleanse method modifies data, make sure to update self.initial_data after calling it, so the rest of the validation process uses the cleaned values.

内容的提问来源于stack exchange，提问作者david