寫個登入系統吧

建立新的app: userAuth

python manage.py userAuth

settings.py INSTALLED_APPS 加入 userAuth

shop/urls.py

...
path('userAuth/', include('userAuth.urls')),
...

登入+登出的route
userAuth/urls.py

from django.urls import path
from userAuth import views

app_name = 'userAuth'
urlpatterns = [
    path('userLogin/', views.userLogin, name='userLogin'),
    path('userLogout/', views.userLogout, name='userLogout')
]

authenticate() django 驗證func
login(request, user) 登入func
logout(request) 登出func

userAuth/views.py

from django.contrib import messages
from django.contrib.auth import authenticate, login, logout
from django.shortcuts import render, redirect
from django.urls import reverse

def userLogin(request):
    if request.method == 'GET':
        return render(request, 'auth/userLogin.html')
    elif request.method == 'POST':
        username = request.POST.get('username')
        password = request.POST.get('password')
        if not username or not password:
            messages.error(request, '請輸入帳號密碼')
            return render(request, 'auth/userLogin.html')

        user = authenticate(request, username=username, password=password)
        if not user:
            messages.error(request, '登入失敗')
            return render(request, 'auth/userLogin.html')
        # user
        login(request, user)
        messages.error(request, '登入成功')
        return redirect(reverse('main:main'))

def userLogout(request):
    logout(request)
    messages.error(request, '登出成功')
    return redirect(reverse('main:main'))

userAuth/templates/userAuth/userLogin.html

{% extends 'main/base.html' %}
{% block content %}
  <h2>登入</h2>
  <form method="post" action="{% url 'userAuth:userLogin' %}">
    {% csrf_token %}
    <p>
      <label for="username">帳號:</label>
      <input id="username" type="text" name="username">
    </p>
    <p>
      <label for="password">密碼:</label>
      <input id="password" type="password" name="password">
    </p>
    <input type="submit" value="登入">
  </form>
{% endblock %}

加上登入與登出的連結

{{ user }} 是預設就會傳的範本變數
user.is_authenticated 回傳True 或 False 是否驗證
main/templates/main/nav.html

...
      <li class="nav-item active">
        {% if not user.is_authenticated %}
          <a class="nav-link" href="{% url 'userAuth:userLogin' %}">登入</a>
        {% else %}
          <a class="nav-link" href="{% url 'userAuth:userLogout' %}">登出</a>
        {% endif %}
      </li>
...

就完成了