django admin在修改obj时使字段为只读,但在添加新obj时需要

from django.contrib import admin

class MyModelAdmin(admin.ModelAdmin):
    readonly_fields = ('field1', 'field2', 'field3')  # 设置需要设为只读的字段

    def get_readonly_fields(self, request, obj=None):
        if obj:  # 如果是修改对象
            return self.readonly_fields + ('field4', 'field5')  # 添加需要额外设为只读的字段
        return self.readonly_fields  # 添加新对象时，所有字段都设为只读

from django.contrib import admin
from .models import MyModel

admin.site.register(MyModel, MyModelAdmin)