django-admin startproject mysite

python manage.py startapp helloapp

from django.shortcuts import render

# Create your views here.

from django.http import HttpResponse
def hello(request):
  return HttpResponse("Hello World! I am coming...")

from django.contrib import admin
from django.urls import path

urlpatterns = [
  path('admin/', admin.site.urls),
]

from django.contrib import admin
from django.urls import path
from helloapp import views　　##引入helloapp这个应用的views（即第3步更改的那个views.py要引入进来才能显示）

urlpatterns = [
  path('index/',views.hello),　　##添加相应的路由（即访问.../index/这样的路径会调用helloapp中定义的那个hello函数而返回相应的response）
  path('admin/', admin.site.urls),
]

python manage.py runserver