Django基础——快速搭建Django项目

配置及环境：Mac Os + Python3.6.2

一、创建一个Django项目

1.使用虚拟环境

#快速创建虚拟环境
python -m venv prjvenv
#激活虚拟环境
source prjvenv/bin/activate

2.创建项目

#安装django
pip install django
#创建项目
django-admin startproject myblog

3.django设置

• myblog/settings.py文件

TIME_ZONE='Asia/Shanghai'

4.数据库迁移

python manage.py migrate

5.启动

python manage.py runserver

二、视图和URL配置

• myblog/views.py文件

from django.http import HttpResponse

#最简单视图
def hello(request):
    return HttpResponse("Hello world")

#带参数的视图
def hours_ahead(request, offset):
       try:
           offset = int(offset)
       except ValueError:
           raise Http404()
       dt = datetime.datetime.now() + datetime.timedelta(hours=offset)
       html = "In %s hour(s), it will be  %s." % (offset, dt)
       return HttpResponse(html)

• myblog/urls.py 文件

from django.conf.urls import url
from django.contrib import admin
from myblog.views import hello
from mysite.views import hours_ahead

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^hello/$',hello),
    url(r'^time/plus/(\d{1,2})/$', hours_ahead),
 ]

三、使用Django模板

1.模板目录配置

• myblog/settings.py文件

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': ['app1/templates','app2/templates'...],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

如果想在项目根目录中放一些主模板(例如在 mysite/templates 目录中)，需要像这样设定 DIRS:
'DIRS': [os.path.join(BASE_DIR, 'templates')],

2.视图函数

from django.shortcuts import render
import datetime

def current_datetime(request):
    now = datetime.datetime.now()
    return render(request, 'current_datetime.html', {'current_date': now})

3.模板文件

• myblog/templates/base.html文件

"-//W3C//DTD HTML 4.01//EN">
"en">

    


    
My helpful timestamp site
    {% block content %}{% endblock %}
    {% block footer %}

    
Thanks for visiting my site.
    {% endblock %}

四、模型

1.配置数据库

• myblog/setting.py

DATABASES = {
    'default': {
    'ENGINE': 'django.db.backends.sqlite3',
    'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
} }

2.创建应用

python manage.py startapp books

3.激活应用

 INSTALLED_APPS = (
        ...
        'books',
)

4.创建模型

• myblogs/books/models.py

from django.db import models

class Publisher(models.Model):
    name = models.CharField(max_length=30)
    address = models.CharField(max_length=50)
    city = models.CharField(max_length=60)
    state_province = models.CharField(max_length=30)
    country = models.CharField(max_length=50)
    website = models.URLField()

    def __str__(self):
        return self.name

class Author(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=40)
    email = models.EmailField()

    def __str__(self):
        return self.last_name


class Book(models.Model):
    title = models.CharField(max_length=100)
    authors = models.ManyToManyField(Author)
    publisher = models.ForeignKey(Publisher,on_delete=models.CASCADE)
    publication_date = models.DateField()

    def __str__(self):
        return self.title

5.迁移数据库

#括号中的内容可以不需要
python manage.py makemigrations (books)
python manage.py migrate

6.操作数据

• 新增数据

方式一：
p1 = Publisher(...)
p1.save()
方式二：
p1 = Publisher.objects.create(...)

• 更新数据

方式一：
p.name = 'Apress Publishing'
p.save()
方式二：
Publisher.objects.filter(id=52).update(name='Apress')   #推荐

• 查询数据

返回查询集合

Publisher.objects.all()
Publisher.objects.filter(name='Apress')    #WHERE name = 'Apress';
Publisher.objects.filter(name__contains="press")     #WHERE name LIKE '%press%';

返回单个对象

Publisher.objects.get(name="Apress")   #不是1个对象就会报异常

try:
    p = Publisher.objects.get(name='Apress')  #数据库中存在一个数据
except Publisher.DoesNotExist:
    print ("Apress isn't in the database yet.")   #数据库中没有数据
else:
    print ("Apress is in the database.")    #有多个数据

• 删除

方式一：单个删除
p = Publisher.objects.get(name="O'Reilly")
p.delete()
方式二：批量删除
Publisher.objects.filter(country='USA').delete()
Publisher.objects.all().delete()

• 排序

方式一：使用order_by()
Publisher.objects.order_by("name", "age")   #根据姓名和年龄排序，-name/-age实现反向排序

方式二：在模型内定义
class Publisher(models.Model):
    ...
    class Meta:
        ordering = ['name']

• 切片

Publisher.objects.order_by('name')[0:2]

五、后台管理

1.创建管理员用户

python manage.py createsuperuser

2.将模型添加到后台管理

• myblog/books/admin.py文件

from django.contrib import admin
from .models import Publisher, Author, Book

admin.site.register(Publisher)
admin.site.register(Author)
admin.site.register(Book)

3.修改模型，使字段在后台输入时变为可选项

• myblog/books/models.py

class Book(models.Model):
    title = models.CharField(max_length=100)
    authors = models.ManyToManyField(Author)
    publisher = models.ForeignKey(Publisher,on_delete=models.CASCADE)
    publication_date = models.DateField(blank=True, null=True)

注意：如果想让日期字段(如 DateField、TimeField、DateTimeField)或数值字段(如 IntegerField、DecimalField、FloatField)接受空值，要同时添加 null=True 和 blank=True。

4.通过模型字段的verbose_name值指定后台显示的字段别名

• myblog/books/models.py

class Author(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=40)
    email = models.EmailField(blank=True, verbose_name='e-mail')

5.自定义修改后台管理列表

• myblog/books/admin.py文件

from django.contrib import admin
from .models import Publisher, Author, Book

#自定义Author的后台管理列表
class AuthorAdmin(admin.ModelAdmin):
        list_display = ('first_name', 'last_name', 'email')  #定义显示字段
        search_fields = ('first_name', 'last_name')    #添加字段搜索

#自定义Book的后台管理列表
class BookAdmin(admin.ModelAdmin):
        list_display = ('title', 'publisher', 'publication_date')    #定义显示字段
        list_filter = ('publication_date',)    #添加时间过滤器
        date_hierarchy = 'publication_date'    #另一种日期过滤器
        ordering = ('-publication_date',)      #排序
        fields = ('title', 'authors', 'publisher', 'publication_date') #自定义修改表单
        filter_horizontal = ('authors',)       #使用选项框(多对多关系时使用)
        raw_id_fields = ('publisher',)         #通过id选择对应选项

admin.site.register(Publisher)
admin.site.register(Author,AuthorAdmin)
admin.site.register(Book,BookAdmin)

六、表单

一、原生表单

1.获取request数据应该try或者设置默认值，防止报错

方式一：
def ua_display_good1(request):
    try:
        ua = request.META['HTTP_USER_AGENT']
    except KeyError:
        ua = 'unknown'
    return HttpResponse("Your browser is %s" % ua)

方式二：
def ua_display_good2(request):
    ua = request.META.get('HTTP_USER_AGENT', 'unknown')
    return HttpResponse("Your browser is %s" % ua)

2.简单的表单提交及表单实例
get和post指向相同的url，根据 if ‘q’ in request.GET:判断是GET还是POST

• 模板页面

#表单页面：myblog/templates/search_form.html


    


    {% if errors %}   #提示错误信息
    

        {% for error in errors %}
        
{{ error }}
        {% endfor %}
    
    {% endif %}

    
"" method="get">  #action为空，表示提交到当前页面
        "text" name="q">
        "submit" value="Search">
    

#结果展示页面：myblog/templates/search_results.html


    


    
You searched for: {{ query }}
    {% if books %}
    
Found {{ books|length }} book{{ books|pluralize }}.
    

        {% for book in books %}
        
{{ book.title }}
        {% endfor %}
    
    {% else %}
    
No books matched your search criteria.
    {% endif %}

• 视图函数:myblog/books/views.py文件

from django.shortcuts import render
from django.http import HttpResponse

def search(request):
    errors = []
    if 'q' in request.GET: # 如果是post,则存在GET['q']
        q = request.GET['q']
        if not q:
            errors.append('Enter a search term.')  # 提交了表单，但是内容为空
        elif len(q) > 20:  # 提交表单，长度超过限制
            errors.append('Please enter at most 20 characters.')
        else:   # 正常提交数据
            books = Book.objects.filter(title__icontains=q)
            return render(request, 'search_results.html',
                {'books': books, 'query': q})

    return render(request, 'search_form.html',{'errors': errors})  #不存在GET['q']说明是GET请求

• 路由：myblog/urls.py文件

urlpatterns = [
    ...
    url(r'^search/$',views.search)
]

二、Django表单模型

1.定义表单类

• myblog/books/forms.py

from django import forms

class ContactForm(forms.Form):
    subject = forms.CharField(max_length=100)  # max_length指定最大长度
    email = forms.EmailField(required=False)
    message = forms.CharField(widget=forms.Textarea) # widget参数，指定表现逻辑，此次指定为文本框

    def clean_message(self):    # 自定义验表单证器
        message = self.cleaned_data['message']
        num_words = len(message.split())
        if num_words < 4:
            raise forms.ValidationError("Not enough words!")
        return message

自定义表单验证器：Django 的表单系统会自动查找名称以 clean_ 开头、以字段名结尾的方法。如果存在这样的方法，在验证过 程中调用。这里，clean_message() 方法会在指定字段的默认验证逻辑(这个 CharField 是必填的)执行完毕 后调用。

2.视图函数

• myblog/books/views.py

from books.forms import ContactForm

def contact(request):
    if request.method == 'POST':
        form = ContactForm(request.POST)
        if form.is_valid():
            cd = form.cleaned_data
            #提示：如果没有配置邮件服务器，调用 send_mail() 时会抛出 ConnectionRefusedError。
            send_mail(
                cd['subject'],
                cd['message'],
                cd.get('email', '[email protected]'),
                ['[email protected]'],
                )
            return HttpResponseRedirect('/contact/thanks/')
    else:
        form = ContactForm(
        initial={'subject': 'I love your site!'}  # 可以初始值
        )
    return render(request, 'contact_form.html', {'form': form})

3.表单页面

• myblogs/templates/contact_form.html

方式一：使用系统默认表单

 
 
    


    
Contact us
    {% if form.errors %}
    
"color: red;">
        Please correct the error{{ form.errors|pluralize }} below.
    
    {% endif %}
    
"" method="post">
    {% csrf_token %}
        
            {{ form.as_table }}
        
        {% csrf_token %}
        "submit" value="Submit">
    

方式二：自定义表单外观样式

    
Contact us
    {% if form.errors %}
    
"color: red;">
        Please correct the error{{ form.errors|pluralize }} below.
    
    {% endif %}
    
"" method="post">
        
class="field">
            {{ form.subject.errors }}
            <label for="id_subject">Subject:
            {{ form.subject }}
        
        
class="field">
            {{ form.email.errors }}
            <label for="id_email">e-mail:
            {{ form.email }}
        
        
class="field">
            {{ form.message.errors }}
            <label for="id_message">Message:
            {{ form.message }}
        
        {% csrf_token %}
        "submit" value="Submit">
    

4.路由设置

• myblogs/myblogs/urls.py

urlpatterns = [
    ...
    url(r'^contact/$', views.contact),
]