I am new to Django and I am doing everything that is indicated in Django documentation but I can not figure out why it keeps saying Page Not Found

我是Django的新手，我正在做Django文档中指出的所有事情，但我不明白为什么它总是说Page Not Found

I tried changing the path or Debug=True to Debug=False but nothing interesting happened. It once worked but now it keeps saying Page Not Found.

我尝试将路径或Debug=True更改为Debug=False，但没有发生任何有趣的事情。它曾经有效，但现在它一直说找不到佩奇。

from django.urls import path

from . import views

urlpatterns = [
    path("mainpage/", views.index, name="index"),
]

this is urls.py mainpage

这是urls.py主页

from django.shortcuts import render


from django.http import HttpResponse


def index(request):
    return HttpResponse("My first page")

this is views.py mainpage

这是views.py主页

from django.contrib import admin
from django.urls import path
from django.contrib import admin
from django.urls import include, path
urlpatterns = [

    path("mainpage/", include("mainpage.urls")),
    path('admin/', admin.site.urls),
]

```and this one is urls.py mysite 

this is the result:
Using the URLconf defined in mysite.urls, Django tried these URL patterns, in this order:

mainpage/ mainpage/ [name='mainpage']
admin/
The current path, mainpage/, didn’t match any of these.

You’re seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.
http://127.0.0.1:8000/mainpage/

I think the way you have set it up the correct url would be mainpage/mainpage.

我认为你设置它的方式正确的网址将是主页/主页。

By having this code path("mainpage/", include("mainpage.urls")) in your project's urls all of your paths found in mainpage.urls will have mainpage/ on the beginning. By including mainpage/ again in the app urls you end up with mainpage/mainpage.

通过在项目的URL中包含此代码路径(“mainPage/”，Include(“mainpage.urls”))，您在mainagee.urls中找到的所有路径的开头都将是mainpage/。通过在应用程序URL中再次包含MainPage/，您最终得到的是MainPage/MainPage。

I hope this is the issue and helps.

我希望这就是问题所在，并有所帮助。