django基本使用（part1）

一、基础安装

安装django

安装数据库PostgreSQL

二、创建项目

django-admin startproject mysite

　三、cd进入mysite文件夹，运行项目

python manage.py runserver 8000

　四、在mysite文件夹 创建应用

python manage.py startapp polls

五、简单显示文本

#第一步：在polls/views下创建视图

from django.http import HttpResponse
def index(request):
    return HttpResponse("Hello, world. You're at the polls index.")

#第二步：为创建的视图创建映射的url.在polls/urls下:

from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),#route:url路径,views:视图,name:代表名称便于引用

]

#第三步：在根路径mysite/urls下注册polls/urls，在mysite/urls.py下：

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

urlpatterns = [
    path('polls/', include('polls.urls')), #include代表路径分发
    path('admin/', admin.site.urls),
]

#第四步：在浏览器中打开http：// localhost：8000 / polls /，将会显示：

Hello, world. You're at the polls index.

六、更改设置文件，在mysite/settings.py中修改数据库的设置

1、数据库的设置

使用sqlite3的数据库设置：

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': 'mydatabase',
    }
}

使用PostgreSQL,必须同时安装psycopg2

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'mydatabase',
        'USER': 'mydatabaseuser',
        'PASSWORD': 'mypassword',
        'HOST': '127.0.0.1',
        'PORT': '5432',
    }
}

2、注册app

在INSTALLED_APPS中默认情况下已包含的应用程序

• django.contrib.admin - 管理网站。你会很快使用它。
• django.contrib.auth - 一个认证系统。
• django.contrib.contenttypes - 内容类型的框架。
• django.contrib.sessions - 会话框架。
• django.contrib.messages - 消息传递框架。
• django.contrib.staticfiles - 一个管理静态文件的框架。

其中一些应用程序至少使用了一个数据库表，所以我们需要在数据库中创建表格，然后才能使用它们，执行命令：

python manage.py migrate

注册自己项目的app:

‘polls.apps.PollsConfig’

七、创建模型

from django.db import models


class Question(models.Model):
    question_text = models.CharField(verbose_name=‘问题描述’,max_length=200)#在admin中显示'问题描述'，而不是question_text,max_length必须设置,默认字段名称为question_text；
    pub_date = models.DateTimeField('date published')#
    #pub_date = models.DateField('date published')
class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)#添加外键
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)#设置默认值

 备注：如何在templets模板中引用字段的verbose_name

fields=Question._meta.fields#将获取所有的字段field对象列表，可以通过遍历

for field in fields:

    print(field.name)   #字段名称，可以通过对象的反射机制获取对应的字段值

    print(field.verbose_name) #获取verbose_name

from django.shortcuts import render
from django.http import HttpResponse,Http404
from django.template import loader
from .models import CompanyList,ReportType,BalanceSheet


# Create your views here.
def index(request):
    objs = BalanceSheet.objects.all()
    exclude_fields = ('id',)
    params = [f for f in BalanceSheet._meta.fields if f.name not in exclude_fields] #obj._meta.fields获取obj所有的字段对象
    import collections
    data = collections.OrderedDict()  #建立有序的字典
    for parm in params:
        values = [getattr(obj, parm.name) for obj in objs]
        data[parm.verbose_name]=values

    context = {
        'data':data,
    }
    return render(request, 'financilaMangement/index.html', context)

八、激活模型

python manage.py makemigrations

python manage.py migrate

九、使用数据库API

#跳入交互式Python shell并使用Django提供的免费API
python manage.py shell

>>> from polls.models import Question, Choice   # Import the model classes we just wrote.

# No questions are in the system yet.
>>> Question.objects.all()
<QuerySet []>

# Create a new Question.
# Support for time zones is enabled in the default settings file, so
# Django expects a datetime with tzinfo for pub_date. Use timezone.now()
# instead of datetime.datetime.now() and it will do the right thing.
>>> from django.utils import timezone
>>> q = Question(question_text="What's new?", pub_date=timezone.now())

# Save the object into the database. You have to call save() explicitly.
>>> q.save()

# Now it has an ID.
>>> q.id
1

# Access model field values via Python attributes.
>>> q.question_text
"What's new?"
>>> q.pub_date
datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>)

# Change values by changing the attributes, then calling save().
>>> q.question_text = "What's up?"
>>> q.save()

# objects.all() displays all the questions in the database.
>>> Question.objects.all()
<QuerySet [<Question: Question object (1)>]>

修改模型，增加__str__方法：

from django.db import models


class Question(models.Model):
    question_text = models.CharField(‘问题描述’,max_length=200)#在admin中显示问题描述，而不是question_text,max_length必须设置；
    pub_date = models.DateTimeField('date published')#
    #pub_date = models.DateField('date published')

    def __str__(self):
        return self.question_text
    


class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)#添加外键
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)#设置默认值
    
    def __str__(self):
        return self.choice_text

    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)

再次运行pythonshell

>>> from polls.models import Question, Choice

# Make sure our __str__() addition worked.
>>> Question.objects.all()
<QuerySet [<Question: What's up?>]>

# Django provides a rich database lookup API that's entirely driven by
# keyword arguments.
>>> Question.objects.filter(id=1)
<QuerySet [<Question: What's up?>]>
>>> Question.objects.filter(question_text__startswith='What')
<QuerySet [<Question: What's up?>]>

# Get the question that was published this year.
>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Question.objects.get(pub_date__year=current_year)
<Question: What's up?>

# Request an ID that doesn't exist, this will raise an exception.
>>> Question.objects.get(id=2)
Traceback (most recent call last):
    ...
DoesNotExist: Question matching query does not exist.

# Lookup by a primary key is the most common case, so Django provides a
# shortcut for primary-key exact lookups.
# The following is identical to Question.objects.get(id=1).
>>> Question.objects.get(pk=1)
<Question: What's up?>

# Make sure our custom method worked.
>>> q = Question.objects.get(pk=1)
>>> q.was_published_recently()
True

# Give the Question a couple of Choices. The create call constructs a new
# Choice object, does the INSERT statement, adds the choice to the set
# of available choices and returns the new Choice object. Django creates
# a set to hold the "other side" of a ForeignKey relation
# (e.g. a question's choice) which can be accessed via the API.
>>> q = Question.objects.get(pk=1)

# Display any choices from the related object set -- none so far.
>>> q.choice_set.all()
<QuerySet []>

# Create three choices.
>>> q.choice_set.create(choice_text='Not much', votes=0)
<Choice: Not much>
>>> q.choice_set.create(choice_text='The sky', votes=0)
<Choice: The sky>
>>> c = q.choice_set.create(choice_text='Just hacking again', votes=0)

# Choice objects have API access to their related Question objects.
>>> c.question
<Question: What's up?>

# And vice versa: Question objects get access to Choice objects.
>>> q.choice_set.all()
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
>>> q.choice_set.count()
3

# The API automatically follows relationships as far as you need.
# Use double underscores to separate relationships.
# This works as many levels deep as you want; there's no limit.
# Find all Choices for any question whose pub_date is in this year
# (reusing the 'current_year' variable we created above).
>>> Choice.objects.filter(question__pub_date__year=current_year)
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>

# Let's delete one of the choices. Use delete() for that.
>>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
>>> c.delete()

十、通过django提供的后台管理进行数据库操作

1、创建一个管理员用户

python manage.py createsuperuser

2、输入用户名、邮箱和密码

Username: admin
Email address: admin@example.com
Password: **********
Password (again): *********
Superuser created successfully.

3、注册项目的相关的数据库，在polls/admin.py 文件中：

from django.contrib import admin

from .models import Question

admin.site.register(Question)

4、重启服务器并打开网址：http://127.0.0.1:8000/admin/并用用户名和密码登陆，便可以看到添加的应用数据库后台。

十一、新增视图-路径-模板

在polls/views.py中：

def detail(request, question_id):
    return HttpResponse("You're looking at question %s." % question_id)

def results(request, question_id):
    response = "You're looking at the results of question %s."
    return HttpResponse(response % question_id)

def vote(request, question_id):
    return HttpResponse("You're voting on question %s." % question_id)

在polls/urls中添加对应的路径

from django.urls import path

from . import views

urlpatterns = [
    # ex: /polls/
    path('', views.index, name='index'),
    # ex: /polls/5/
    path('<int:question_id>/', views.detail, name='detail'),
    # ex: /polls/5/results/
    path('<int:question_id>/results/', views.results, name='results'),
    # ex: /polls/5/vote/
    path('<int:question_id>/vote/', views.vote, name='vote'),#尖括号中的文字用于捕获url中的传递的值，并以关键字参数question_id=5传递给视图函数（views）
]

通过数据库api在视图中返回数据库中的数据，在polls/views中修改index视图函数：

from django.http import HttpResponse

from .models import Question


def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]#返回queryset对象，共5个，每个对象代表一行数据。
    output = ', '.join([q.question_text for q in latest_question_list])#通过列表生成式将上述5个对象question_text连接起来生成字符串
    return HttpResponse(output)

# Leave the rest of the views (detail, results, vote) unchanged

views通过调用template中的模板来返回数据

在templates中创建一个文件夹与项目名相同：polls,在templates/polls下创建一个模板文件，命名为index.html

在index.html中输入：

{% if latest_question_list %}
    <ul>
    {% for question in latest_question_list %}
        <li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>#模板中使用.来引用变量属性
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}

修改views中的index函数，使用render返回模板，模板使用的参数；

from django.shortcuts import render

from .models import Question


def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]
    context = {'latest_question_list': latest_question_list}
    return render(request, 'polls/index.html', context)

返回404错误

from django.http import Http404
from django.shortcuts import render

from .models import Question
# ...
def detail(request, question_id):
    try:
        question = Question.objects.get(pk=question_id)
    except Question.DoesNotExist:
        raise Http404("Question does not exist")
    return render(request, 'polls/detail.html', {'question': question})

简写返回404错误，get和get_object_or_404经常使用，filter和get_list_or_404成对使用：

from django.shortcuts import get_object_or_404, render

from .models import Question
# ...
def detail(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/detail.html', {'question': question})

将模板中的地址引用改为松耦合状态

{% if latest_question_list %}
    <ul>
    {% for question in latest_question_list %}
        #<li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>#模板中使用.来引用变量属性
        <li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li>#来源于urlconfig中的name,这样在更改url时就不需要对模板中引用的url进行修改了
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}

更进一步：由于一个django中可能有多个的应用程序，如果两个应用程序的urlconfig中都设置了name='detail'时，模板回产生引用混乱，因此，需要在模板和urlconfig中加入appname,以便区分

在polls/urls中修改为：

from django.urls import path

from . import views

app_name = 'polls'
urlpatterns = [
    path('', views.index, name='index'),
    path('<int:question_id>/', views.detail, name='detail'),
    path('<int:question_id>/results/', views.results, name='results'),
    path('<int:question_id>/vote/', views.vote, name='vote'),
]

在templates/polls/index.html中修改为：

{% if latest_question_list %}
    <ul>
    {% for question in latest_question_list %}
        #<li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>#模板中使用.来引用变量属性
        #<li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li>#来源于urlconfig中的name,这样在更改url时就不需要对模板中引用的url进行修改了
        <li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}