Develop Reference

How do i make my categories function correctly?

so im trying to seperate my blog posts into different categories but right now it all just appears as my username
blogcategory.html
{% extends "base.html" %}
{% block page_content %}
<div class="col-md-8 offset-md-2">
<h1>{{ category | title }}</h1>
<hr>
{% for post in posts %}
<h2>{{ post.title }}</h2>
<small>
{{ post.created_on.date }} |
Categories:
{% for category in post.categories.all %}
<a href="{% url 'blogcategory' category.name %}">
{{ category.name }}
</a>
{% endfor %}
</small>
<p>{{ post.body | slice:":400" }}...</p>
{% endfor %}
</div>
{% endblock %}
blogdetail.html
{% extends "base.html" %}
{% block page_content %}
<div class="col-md-8 offset-md-2">
<h1>{{ post.title }}</h1>
<small>
{{ post.created_on.date }} |
Categories:
{% for category in post.categories.all %}
<a href="{% url 'blogcategory' category.name %}">
{{ category.name }}
</a>
{% endfor %}
</small>
<p>{{ post.body | linebreaks }}</p>
<h3>Leave a comment:</h3>
<form action="/blog/{{ post.pk }}/" method="post">
{% csrf_token %}
<div class="form-group">
{{ user.username|default:'Guest' }}
</div>
<div class="form-group">
{{ form.body }}
</div>
<button type="submit" class="btn btn-primary">Submit</button>
</form>
<h3>Comments:</h3>
{% for comment in comments %}
<p>
On {{comment.created_on.date }}
<b>{{ user.username|default:'Guest'}}</b> wrote:
</p>
<p>{{ comment.body }}</p>
<hr>
{% endfor %}
</div>
{% endblock %}
blogindex
{% extends "base.html" %}
{% block page_content %}
<div class="col-md-8 offset-md-2">
<h1>Blog Index</h1>
<hr>
{% for post in posts %}
<h2>{{ post.title }}</h2>
<small>
{{ post.created_on.date }} |
Categories:
{% for category in post.categories.all %}
<a href="{% url 'blogcategory' category.name %}">
{{ category.name }}
</a> blo
{% endfor %}
</small>
<p>{{ post.body | slice:":400" }}...</p>
{% endfor %}
</div>
{% endblock %}
models.py
from django.db import models
class Category(models.Model):
name = models.CharField(max_length=20)
class Post(models.Model):
title = models.CharField(max_length=255)
body = models.TextField()
created_on = models.DateTimeField(auto_now_add=True)
last_modified = models.DateTimeField(auto_now=True)
categories = models.ManyToManyField("Category", related_name="posts")
class Comment(models.Model):
author = models.CharField(max_length=180)
body = models.TextField()
created_on = models.DateTimeField(auto_now_add=True)
post = models.ForeignKey("Post", on_delete=models.CASCADE)
views.py
from django.shortcuts import render
from .forms import CommentForm
from .models import Post, Comment
def blogindex(request):
posts = Post.objects.all().order_by("-created_on")
context = {"posts": posts}
return render(request, "blogindex.html", context)
def blogcategory(request, category):
posts = Post.objects.filter(
categories__name__contains=category
).order_by(
'-created_on'
)
context = {
"category": category,
"posts": posts
}
return render(request, "blog_category.html", context)
def blogdetail(request, pk):
post = Post.objects.get(pk=pk)
comments = Comment.objects.filter(post=post)
form = CommentForm()
if request.method == "POST":
form = CommentForm(request.POST)
if form.is_valid():
comment = Comment(
author=form.cleaned_data["author"],
body=form.cleaned_data["body"],
post=post,
)
comment.save()
context = {"post": post, "comments": comments, "form": form}
return render(request, "blogdetail.html", context)
realistically i should be able to make post be of certain categories and click on those categories when i see them. But for some reason, the categories default to the username aof the person who made it and cant be changed. Please help.

The 'header_image' attribute has no file associated with it

When I create a new post with an image, everything is fine, but if I edit it, I want to delete the image using the "clear" button, then this error appears, and if I change, then nothing changes, but there are no errors
here is models.py
`
from django.db import models
from django.urls import reverse
class Post(models.Model):
title = models.CharField(max_length=200)
author = models.ForeignKey(
'auth.User',
on_delete=models.CASCADE,
)
body = models.TextField()
header_image = models.ImageField(blank=True, null=True, upload_to="images/", default='#') #new
def __str__(self):
return self.title
def get_absolute_url(self):
return reverse('post_detail', args=[str(self.id)])`
here is views.py
`
from django.shortcuts import render
from django.views.generic import ListView, DetailView
from django.views.generic.edit import CreateView, UpdateView, DeleteView
from django.urls import reverse_lazy
from .models import Post
class BlogListView(ListView):
model = Post
template_name = 'home.html'
class BlogDetailView(DetailView):
model = Post
template_name = 'post_detail.html'
class BlogCreateView(CreateView):
model = Post
template_name = 'post_new.html'
fields = ['title', 'author', 'body', 'header_image']
class BlogUpdateView(UpdateView):
model = Post
template_name = 'post_edit.html'
fields = ['title', 'body', 'header_image']
class BlogDeleteView(DeleteView):
model = Post
template_name = 'post_delete.html'
success_url = reverse_lazy('home')
#property
def image_url(self):
"""
Return self.photo.url if self.photo is not None,
'url' exist and has a value, else, return None.
"""
if self.image:
return getattr(self.photo, 'url', None)
return None`
post_base.html
`{% load static %}
<html>
<head>
<title>Django blog</title>
<link href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:400"
rel="stylesheet">
<link href="{% static 'css/base.css' %}" rel="stylesheet">
</head>
<body>
<div>
<header>
<div class="nav-left">
<h1>Django blog</h1>
<h2>Admin</h2>
</div>
<div class="nav-right">
+ New Blog Post
</div>
</header>
{% if user.is_authenticated %}
<p>Hi {{ user.username }}!</p>
{% else %}
<p>You are not logged in.</p>
Log In<br>
<p>Sign up</p>
{% endif %}
{% block content %}
{% endblock content %}
</div>
</body>
</html>`
post_detail.html
`
{% extends 'base.html' %}
{% block content %}
<div class="post-entry">
<h2>{{ post.title }}</h2>
<p>{{ post.body }}</p>
</div>
<p>+ Edit Blog Post</p>
<p>+ Delete Blog Post</p>
<img src="{{ post.header_image.url|default_if_none:'#' }}">
{{ post.body|safe }}
{% endblock content %}`
post_new.html
`
{% extends 'base.html' %}
{% block content %}
<h1>New post</h1>
<form action="" method="post" enctype="multipart/form-data">{% csrf_token %}
{{ form.as_p }}
<input type="submit" value="Save" />
</form>
{% endblock content %}`
post_edit.html
`
{% extends 'base.html' %}
{% block content %}
<h1>Edit post</h1>
<form action="" method="post">{% csrf_token %}
{{ form.as_p }}
<input type="submit" value="Update" />
</form>
{% endblock content %}`

enctype='multipart/form-data' means that no characters will be encoded. that is why this type is used while uploading files to server. So multipart/form-data is used when a form requires binary data, like the contents of a file, to be uploaded.
You forgot to add enctype='multipart/form-data' in your post_edit.html form and that's the reason your files aren't sent to Django. Following code should work.
post_edit.html
{% extends 'base.html' %}
{% block content %}
<h1>Edit post</h1>
<form action="" method="post" enctype='multipart/form-data'>
{% csrf_token %}
{{ form.as_p }}
<input type="submit" value="Update" />
</form>
{% endblock content %}

NoReverseMatch at /blog/ - Django by example code list and detail view issue

`I'm working on the code in chapter 1 of the django by example. Followed all instructions and reviewed many feedbacks on this site and other areas but not to my luck. I had earlier attempted get_absolute_url and return reverse method unsuccessfully. I was trying an instructed approach and land exactly the same issues in listview and detailview. I'm a beginner so I guess I'm missing something may be fundamental. Is there any version dependency. I've installed latest django and python. Need advice and thanks for any help!
This is the error message
models.py
from django.db import models
from django.utils import timezone
from django.contrib.auth.models import User
from django.urls import reverse
# Create your models here.
class PublishedManager(models.Manager):
def get_queryset(self):
return super().get_queryset().filter(status='published')
class Post(models.Model):
STATUS_CHOICES = (
('draft', 'Draft'),
('published', 'Published'),
)
title = models.CharField(max_length=250)
slug = models.SlugField(max_length=250, unique_for_date='publish_date')
author = models.ForeignKey(User, on_delete=models.CASCADE, related_name='blog_posts')
body = models.TextField()
publish_date = models.DateTimeField(default=timezone.now)
created_date = models.DateTimeField(auto_now_add=True)
updated_date = models.DateTimeField(auto_now_add=True)
status = models.CharField(max_length=10, choices=STATUS_CHOICES, default='draft')
objects = models.Manager() # default Manager
published = PublishedManager() # our custom manager
class Meta:
ordering = ['-publish_date',]
def __str__(self):
return self.title
def get_absolute_url(self):
return reverse(
'blog:post_detail',
args=[
self.publish_date.year,
self.publish_date.month,
self.publish_date.day,
self.slug,
]
)
views.py
from django.shortcuts import render, get_object_or_404
from .models import Post
def post_list(request):
posts = Post.published.all()
return render(request, 'blog/post/post_list.html', {'posts':posts})
def post_detail(request, year, month, day, post):
post = get_object_or_404(Post, slug=post,
status='published',
publish_date__year=year,
publish_date__month=month,
publish_date__day=day)
return render(request, 'blog/post/post_detail.html',{'post':post})
urls.py ( For app)
from django.urls import path
from . import views
app_name = 'blog'
urlpatterns = [
#post views
path('', views.post_list, name='post_list'),
path('<int:year>/<int:month>/<int=day>/<slug=post>/',
views.post_detail,
name='post_detail'),
]
admin.py
from django.contrib import admin
from .models import Post
#admin.register(Post)
class PostAdmin(admin.ModelAdmin):
list_display = ('title', 'slug', 'author', 'publish_date', 'status')
list_filter = ('status', 'created_date','publish_date', 'author')
search_fields = ('title', 'body')
prepopulated_fields = {'slug':('title',)}
raw_id_fields = ('author',)
date_hierarchy = 'publish_date'
ordering = ('status', 'publish_date')
post_detail.html
{% extends "blog/base.html" %}
{% block title %}{{post.title}}{% endblock %}
{% block content %}
<h> {{post.title}} </h>
<p class="date">
Published {{ post.publish_date }} by {{ post.author }}
</p>
{{ post.body|linebreaks }}
{%endblock%}
post_list.html
{% extends "blog/base.html" %}
{% block title %}My Blog{% endblock %}
{% block content %}
<h1>My Blog</h1>
{% for post in posts %}
<h2>
<a href="{% url 'blog:post_list' post.title %}"
{{ post.title }}
</a>
</h2>
<p class="date">
Published {{ post.publish_date }} by {{ post.author }}
</p>
{{ post.body|truncatewords:30|linebreaks }}
{% endfor %}
{% endblock %}
Modified post_list.html
{% extends "blog/base.html" %}
{% block title %}My Blog{% endblock %}
{% block content %}
<h1>My Blog</h1>
{% for post in posts %}
<h2>
{% url 'blog:post_detail' post.publish_date.year post.publish_date.month post.publish_date.day post.publish_date.slug as post.title %}
<a href="{{ post.title }}">
{{ post.title }}
</a>
</h2>
<p class="date">
Published {{ post.publish_date }} by {{ post.author }}
</p>
{{ post.body|truncatewords:30|linebreaks }}
{% endfor %}
{% endblock %}

in your post_list.html
change this
<a href="{% url 'blog:post_list' post.title %}"
to
<a href="{% url 'blog:post_list'%}"
your url doesn't accept an argument but you are passing an argument from your template.

How to limit the number of items displayed in Django app

I have this Django model in my newspaper app:
class Article(models.Model):
title = models.CharField(max_length=255)
body = models.TextField()
date = models.DateTimeField(auto_now_add=True)
author = models.ForeignKey(
get_user_model(),
on_delete=models.CASCADE,
)
def __str__(self):
return self.title
def get_absolute_url(self):
return reverse('article_detail', args=[str(self.id)])
It currently displays all articles but I want to limit what is displayed to the 3 most recent articles. How is that done?
This is my view:
class ArticleListView(LoginRequiredMixin, ListView):
model = Article
template_name = 'article_list.html'
login_url = 'login'
This is the html template:
{% extends 'base.html' %}
{% block title %}Articles{% endblock title %}
{% block content %}
{% for article in object_list %}
<div class="card">
<div class="card-header">
<span class="font-weight-bold">{{ article.title }}</span> ·
<span class="text-muted">by {{ article.author }} | {{ article.date }}</span>
</div>
<div class="card-body">
<p>{{ article.body }}</p>
Edit
Delete
</div>
<div class="card-footer">
{% for comment in article.comments.all %}
<p>
<span class="font-weight-bold">{{ comment.author }} ·</span>
{{ comment }}
</p>
{% endfor %}
</div>
</div>
<br />
{% endfor %}
{% endblock content %}

In your (assumed) ListView you should define the queryset, something like
class ArticleListView(LoginRequiredMixin, ListView):
model = Article
template_name = 'article_list.html'
login_url = 'login'
queryset = Article.objects.order_by('-date')[:3]
More on this here.

NoReverseMatch at /blog/

I am following "django by example"
and i met the problem but i don't know what causes it.
The following is the error page:
NoReverseMatch at /blog/
Reverse for 'post_detail' with arguments '('', '', '')' not found. 1 pattern(s) tried: ['blog/(?P\d{4})/(?P\d{2})/(?P\d{2})/(?P[-\w]+)/$']
Request Method:
GET
Request URL:
http://127.0.0.1:8000/blog/
Django Version:
1.11
Exception Type:
NoReverseMatch
Exception Value:
Reverse for 'post_detail' with arguments '('', '', '')' not found. 1 pattern(s) tried: ['blog/(?P\d{4})/(?P\d{2})/(?P\d{2})/(?P[-\w]+)/$']
Exception Location:
E:\workspace\pycharm\djangobyexample\mysite\env\lib\site-packages\django\urls\resolvers.py in _reverse_with_prefix, line 497
Python Executable:
E:\workspace\pycharm\djangobyexample\mysite\env\Scripts\python.exe
Python Version:
3.5.2
Python Path:
['E:\workspace\pycharm\djangobyexample\mysite',
'E:\workspace\pycharm\djangobyexample\mysite\env\Scripts\python35.zip',
'E:\workspace\pycharm\djangobyexample\mysite\env\DLLs',
'E:\workspace\pycharm\djangobyexample\mysite\env\lib',
'E:\workspace\pycharm\djangobyexample\mysite\env\Scripts',
'c:\users\richard\appdata\local\programs\python\python35\Lib',
'c:\users\richard\appdata\local\programs\python\python35\DLLs',
'E:\workspace\pycharm\djangobyexample\mysite\env',
'E:\workspace\pycharm\djangobyexample\mysite\env\lib\site-packages']
Main URLConfiguration
urlpatterns = [
url(r'^admin/', admin.site.urls),
url(r'^blog/', include('blog.urls', namespace='blog', app_name='blog')),
]
blog/url.py
from django.conf.urls import url
from . import views
urlpatterns = [
# post views
# url(r'^$', views.post_list, name='post_list'),
url(r'^$', views.PostListView.as_view(), name='post_list'),
url(r'^(?P<year>\d{4})/(?P<month>\d{2})/(?P<day>\d{2})/(?P<post>[-\w]+)/$',
views.post_detail,
name='post_detail'),
#url(r'^(?P<post_id>\d+)/share/$', views.post_share, name='post_share'),
]
views.py
from django.shortcuts import render, get_object_or_404
from .models import Post
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
from django.views.generic import ListView
from .forms import EmailPostForm
from django.core.mail import send_mail
# Create your views here.
class PostListView(ListView):
queryset = Post.published.all()
context_object_name = 'posts'
paginate_by = 3
template_name = 'blog/post/list.html'
def post_detail(request, year, month, day, post):
post = get_object_or_404(Post, slug=post,
status='published',
publish__year=year,
publish__month=month,
publish__day=day)
return render(request, 'blog/post/detail.html', {'post': post})
models.py
from django.db import models
from django.utils import timezone
from django.contrib.auth.models import User
from django.core.urlresolvers import reverse
class PublishedManager(models.Manager):
def get_query(self):
return super(PublishedManager, self).get_query().filter(status='published')
class Post(models.Model):
STATUS_CHOICES = {
('draft', 'Draft'),
('published', 'Published'),
}
title = models.CharField(max_length=250, primary_key=True)
slug = models.SlugField(max_length=250, unique_for_date='publish')
author = models.ForeignKey(User, related_name='blog_post')
body = models.TextField()
publish = models.DateTimeField(default=timezone.now)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
status = models.CharField(max_length=10, choices=STATUS_CHOICES, default='draft')
class Meta:
# Telling django to sort results by the publish field in descending order by default when we query the database
ordering = ('-publish',)
def __str__(self):
return self.title
objects = models.Manager()
published = PublishedManager()
def get_absolute_url(self):
return reverse('blog:post_detail', args=[self.publish.year,
self.publish.strftime('%m'),
self.publish.strftime('%d'),
self.slug])
detail.html
{% extends "blog/base.html" %}
{% block title %}{{ post.title }}{% endblock %}
{% block content %}
<h1>{{ post.title }}</h1>
<p class="date">
Published {{ post.publish }} by {{ post.author }}
</p>
{{ post.body|linebreaks }}
{% endblock %}
list.html
{% extends "blog/base.html" %}
{% block title %}My Blog{% endblock %}
{% block content %}
<h1>My Blog</h1>
{% for post in posts %}
<h2>
<a href="{{ post.get_absolute_url }}">
{{ post.title }}
</a>
</h2>
<p class="date">
Published {{ post.publish }} by {{ post.author }}
</p>
{{ post.body|truncatewords:30|linebreaks }}
{% endfor %}
{% include "pagination.html " with page=page_obj %}
{% endblock %}
base.html
{% load staticfiles %}
<html>
<head>
<meta charset="UTF-8">
<title>{% block title %}{% endblock %}</title>
</head>
<body>
<div id="content">
{% block content %}
{% endblock %}
</div>
<div id="sidebar">
<h2>My blog</h2>
<p>This is my blog.</p>
</div>
</body>
</html>

This line is giving you the error, because the arguments are invalid.
<!-- <a href="{% url 'blog:post_detail' post.year post.month post.day %}">-->
The post does not have year, month and day attributes -- they are attributes of post.publish.
You are already using {{ post.get_absolute_url }} on the next line of the template to get the url. Since the url tag line is inside an html comment <!-- -->, the easiest fix is to simply delete the line.