模板渲染期间Django管理站点中的错误-'__str__返回了非字符串（类型字节）'

Question

我想在Django应用的管理面板中访问模型-http://127.0.0.1:8000/admin/scraper/ad_history/

当我单击模型链接以查看其条目时，出现以下错误：

TypeError at /admin/scraper/ad_history/
__str__ returned non-string (type bytes)
Request Method: GET
Request URL:    http://127.0.0.1:8000/admin/scraper/ad_history/
Django Version: 2.1
Exception Type: TypeError
Exception Value:    
__str__ returned non-string (type bytes)
Exception Location: C:\Python36-32\lib\site-packages\django\contrib\admin\templatetags\admin_list.py in items_for_result, line 251
Python Executable:  C:\Python36-32\Anaconda\python.exe
Python Version: 3.6.5
Python Path:    
['C:\\MyApp\\MyApp',
 'C:\\Python36-32\\python36.zip',
 'C:\\Python36-32\\DLLs',
 'C:\\Python36-32\\lib',
 'C:\\Python36-32',
 'C:\\Python36-32\\lib\\site-packages',
 'C:\\Python36-32\\lib\\site-packages\\win32',
 'C:\\Python36-32\\lib\\site-packages\\win32\\lib',
 'C:\\Python36-32\\lib\\site-packages\\Pythonwin']
Server time:    Tue, 21 Aug 2018 14:05:36 +0000

__str__ returned non-string (type bytes)

广告历史记录模型：

class Ad_History(models.Model):
    ad = models.ForeignKey(Ad, on_delete=models.CASCADE)
    date_found = models.DateTimeField(auto_now_add=True, blank=True)
    keyword = models.ForeignKey(Keyword, null=True, on_delete=models.CASCADE)
    kw_scrape_count = models.IntegerField()
    page_found = models.IntegerField(default=None, null=True)
    sequence = models.IntegerField(default=None, null=True)

    def __str__(self):
        return self.ad.description

Admin.py：

from django.contrib import admin
from .models import Domain, Ad, Phone, Email, Hour, Address, Ad_History 

from scraper.forms import AdHistoryAdmin, AdAdmin, DomainAdmin

# Register your models here.
admin.site.register(Domain, DomainAdmin)
admin.site.register(Phone)
admin.site.register(Email)
admin.site.register(Address)
admin.site.register(Hour)
admin.site.register(Ad, AdAdmin)
admin.site.register(Ad_History, AdHistoryAdmin)

AdHistoryAdmin：

class AdHistoryAdmin(admin.ModelAdmin):
    list_display = ('ad', 'date_found', 'kw_scrape_count', 'keyword', 'sequence')

我试图更改模型中的 str 函数以返回虚拟字符串（以确保没有字节被返回），但这仍然会产生错误。

有什么想法可以使我深究吗？

Answer 1

我不确定您要输入什么到字符串中，但是使用非字符串值可以做到这一点：

def __str__(self):
   return 'Value1={0}, Value2={1}'.format(self.value1, self.value2)