基础程序设计（投票系统的设计）--django

前提：1.Django 需要 Python（Download Python | Python.orgThe official home of the Python Programming Languagehttps://www.python.org/downloads/）

2.安装django，可以在自己虚拟环境中，使用pip，输入以下命令

python -m pip install Django

注：如果想要快速开发可以采用flask进行，本章主要讲利用成熟且流行的django进行开发。

一.创建项目

在Windows的命令提示符窗口中执行下面的命令

django-admin startproject myDjango

注：命令在D盘根目录中创建一个名称为myDjango的项目。django-admin将为项目创建一个名为myDjango文件夹，并在其中创建项目的其他文件。

二.确认项目创建成功，或者在后面判断代码正确与否，都可以使用

但一定要在mydjango的目录下输入

python manage.py runserver

如果不成功，可以写成python -m pip install Django 8000

成功后显示

三.创建投票系统

1.即然是投票应用，你需要输入以下命令

python manage.py startapp polls

2.接下来开始完善polls系统，代码都需要在polls呈现

?polls/views.py（views是视图呈现）

from django.http import HttpResponse


def index(request):
    return HttpResponse("Hello, world.")

polls/url.py（每创建一个视图，都需要在urls进行映射,有了这个框架，可以每次用path在下面添加，这个需要你自己创建）

from django.urls import path
from . import views


app_name = 'polls'
urlpatterns = [
    path('', views.IndexView.as_view(), name='index'),

]

毕竟这是投票应用的映射，你还需要去mydjango/url.py进行

mysite/urls.py?
from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path("polls/", include("polls.urls")),
    
]

3.设置数据库

数据库都是django自己带的，可以在mydjango/setting.py查看，如果想更改数据库，在（DATABASES）这更改。

另外还需要在mydjango/setting.py/INSTALLED_APPS这插入polls

我们常常在数据库中添表（也就是需要来构造投票系统怎么布局）

在polls/models.py文件中进行定义类

import datetime

from django.contrib import admin
from django.db import models
from django.utils import timezone
# Create your models here.
class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    def __str__(self):
        return self.question_text

    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)
# 不确定admin是自己的名字还是admin
    @admin.display(
        boolean=True,
        ordering='pub_date',
        description='Published recently?',
        )
    def was_published_recently(self):
        now = timezone.now()
        return now - datetime.timedelta(days=1) <= self.pub_date <= now

list_filter = ['pub_date']
search_fields = ['question_text']

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __str__(self):
        return self.choice_text

?定义类（class）之后需要在当前目录的终端执行下面两条命令，才使得把类传递到数据库中，记住你买一次改或者添加删除都需要执行下面两个命令。

 python manage.py makemigrations

 python manage.py migrate

每迁移一次，会出现这个，这个可以不用管

4.创建管理员账号

python manage.py createsuperuser

根据你的需要进行编写,你为了能在浏览器看到，你必须添加path路径

最后在终端运行

python manage.py runserver

输入Site administration | Django site admin

进行查看

5.向管理页面加入投票应用?polls/admin.py

from django.contrib import admin

from .models import Question

admin.site.register(Question)

此时你可以去编辑和填写相关内容

7.修改视图polls/views

我们知道views，就是窗户，我们可以不用在视图写hello world，可以去导入html文件

需要你在在你的?polls?目录里创建一个?templates?目录

接着改变views

from django.http import HttpResponse,HttpResponseRedirect
from django.shortcuts import get_object_or_404, render
from django.urls import reverse
from django.views import generic
from django.utils import timezone

from .models import Choice, Question

class IndexView(generic.ListView):
    template_name = 'polls/index.html'
    context_object_name = 'latest_question_list'

    def get_queryset(self):
        """Return the last five published questions."""
        return Question.objects.order_by('-pub_date')[:5]

class DetailView(generic.DetailView):
    model = Question
    template_name = 'polls/detail.html'

    def get_queryset(self):
        """
        Excludes any questions that aren't published yet.
        """
        return Question.objects.filter(pub_date__lte=timezone.now())


class ResultsView(generic.DetailView):
    model = Question
    template_name = 'polls/results.html'


def get_queryset(self):
    """
    Return the last five published questions (not including those set to be
    published in the future).
    """
    return Question.objects.filter(
    pub_date__lte=timezone.now()
    ).order_by('-pub_date')[:5]


def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))

在templates建立三个html

三个html的内容可以去【免费】基于django的基础程序设计的三个html文件资源-CSDN文库https://download.csdn.net/download/2301_76329581/88762115

此时会报错

这时要求修改polls/urls

from django.urls import path
from . import views


app_name = 'polls'
urlpatterns = [
    path('', views.IndexView.as_view(), name='index'),
    path('<int:pk>/', views.DetailView.as_view(), name='detail'),
    path('<int:pk>/results/', views.ResultsView.as_view(), name='results'),
    path('<int:question_id>/vote/', views.vote, name='vote'),

]

?也要在mydjango/urls/

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

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

也要在polls/admin

from django.contrib import admin
from .models import Choice,Question

class ChoiceInline(admin.StackedInline):
    model = Choice
    extra = 3
class QuestionAdmin(admin.ModelAdmin):
    fieldsets = [
        (None, {'fields': ['question_text']}),
        ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
    ]
    inlines = [ChoiceInline]

    list_display = ('question_text', 'pub_date', 'was_published_recently')


admin.site.register(Question, QuestionAdmin)
admin.site.register(Choice)

?也要在polls/models.py

import datetime

from django.contrib import admin
from django.db import models
from django.utils import timezone
# Create your models here.
class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    def __str__(self):
        return self.question_text

    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)
# 不确定admin是自己的名字还是admin
    @admin.display(
        boolean=True,
        ordering='pub_date',
        description='Published recently?',
        )
    def was_published_recently(self):
        now = timezone.now()
        return now - datetime.timedelta(days=1) <= self.pub_date <= now

list_filter = ['pub_date']
search_fields = ['question_text']

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __str__(self):
        return self.choice_text

在polls/test.py

# Create your tests here.
import detail

from django.test import TestCase
from django.utils import timezone

from .models import Question
from django.urls import reverse

def create_question(question_text, days):
    """
    Create a question with the given `question_text` and published the
    given number of `days` offset to now (negative for questions published
    in the past, positive for questions that have yet to be published).
    """
    time = timezone.now() + datetime.timedelta(days=days)
    return Question.objects.create(question_text=question_text, pub_date=time)
class QuestionIndexViewTests(TestCase):
    def test_no_questions(self):
        """
        If no questions exist, an appropriate message is displayed.
        """
        response = self.client.get(reverse('polls:index'))
        self.assertEqual(response.status_code, 200)
        self.assertContains(response, "No polls are available.")
        self.assertQuerysetEqual(response.context['latest_question_list'], [])
    def test_past_question(self):
        """
        Questions with a pub_date in the past are displayed on the
        index page.
        """
        question = create_question(question_text="Past question.", days=-30)
        response = self.client.get(reverse('polls:index'))
        self.assertQuerysetEqual(
            response.context['latest_question_list'],
            [question],
        )
    def test_future_question(self):
        """
        Questions with a pub_date in the future aren't displayed on
        the index page.
        """
        create_question(question_text="Future question.", days=30)
        response = self.client.get(reverse('polls:index'))
        self.assertContains(response, "No polls are available.")
        self.assertQuerysetEqual(response.context['latest_question_list'], [])

        """
        The detail view of a question with a pub_date in the future
        returns a 404 not found.
        """
        future_question = create_question(question_text='Future question.', days=5)
        url = reverse('polls:detail', args=(future_question.id,))
        response = self.client.get(url)
        self.assertEqual(response.status_code, 404)

    def test_future_question_and_past_question(self):
        """
        Even if both past and future questions exist, only past questions
        are displayed.
        """
        question = create_question(question_text="Past question.", days=-30)
        create_question(question_text="Future question.", days=30)
        response = self.client.get(reverse('polls:index'))
        self.assertQuerysetEqual(
            response.context['latest_question_list'],
            [question],
        )
    def test_two_past_questions(self):
        """
        The questions index page may display multiple questions.
        """
        question1 = create_question(question_text="Past question 1.", days=-30)
        question2 = create_question(question_text="Past question 2.", days=-5)
        response = self.client.get(reverse('polls:index'))
        self.assertQuerysetEqual(
            response.context['latest_question_list'],
            [question2, question1],
        )
    def test_past_question(self):
        """
        The detail view of a question with a pub_date in the past
        displays the question's text.
        """
        past_question = create_question(question_text='Past Question.', days=-5)
        url = reverse('polls:detail', args=(past_question.id,))
        response = self.client.get(url)
        self.assertContains(response, past_question.question_text)

?在polls/view

from django.http import HttpResponse,HttpResponseRedirect
from django.shortcuts import get_object_or_404, render
from django.urls import reverse
from django.views import generic
from django.utils import timezone

from .models import Choice, Question

class IndexView(generic.ListView):
    template_name = 'polls/index.html'
    context_object_name = 'latest_question_list'

    def get_queryset(self):
        """Return the last five published questions."""
        return Question.objects.order_by('-pub_date')[:5]

class DetailView(generic.DetailView):
    model = Question
    template_name = 'polls/detail.html'

    def get_queryset(self):
        """
        Excludes any questions that aren't published yet.
        """
        return Question.objects.filter(pub_date__lte=timezone.now())


class ResultsView(generic.DetailView):
    model = Question
    template_name = 'polls/results.html'


def get_queryset(self):
    """
    Return the last five published questions (not including those set to be
    published in the future).
    """
    return Question.objects.filter(
    pub_date__lte=timezone.now()
    ).order_by('-pub_date')[:5]


def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))

8.应用界面设置

同时在style.css写下

li a {
    color: green;
}
body {
    background: white url("images/background.gif") no-repeat;

}

最后在?

Add question | Django site adminhttp://127.0.0.1:8000/admin/polls/question/add/

源代码显示处

?