title: Post matching query does not exist. - Django error while trying to access URL of other pages
body: <p>Everything was okay till I created a blog app in my Django projects, now when I try to access the other apps(pages) on the website, it gives me this error.
  I can't access the URLs under the other apps, I can only access the URLs under the blog</p>
  <h2>blog/views.py</h2>
  <pre><code>from django.shortcuts import render, redirect
  from .models import Post
  from .forms import commentform
  
  def blog(request):
      posts = Post.objects.all(pk=id)
      return render(request, 'blog.html', {'posts': posts})
  
  def howtouse(request):
      return render(request, 'howtouse.html')
  
  def full_post(request, slug):
      post = Post.objects.get(slug=slug)
      if request.method == 'POST':
          form = commentform(request.POST)
  
          if form.is_valid():
              comment = form.save(commit=False)
              comment.post = post
              comment.save()
  
              return redirect('full_post', slug=post.slug)
      else:
          form = commentform()
      return render(request, 'full_post.html', {'post': post, 'form': form})
  </code></pre>
  <h2>blog/models.py</h2>
  <pre><code>from django.db import models
  
  class Post(models.Model):
      title = models.CharField(max_length=255)
      slug = models.SlugField()
      intro = models.TextField()
      body = models.TextField()
      date_added = models.DateTimeField(auto_now_add=True)
  
      class Meta:
          ordering = ['-date_added']
  
  
  class Comments(models.Model):
      post = models.ForeignKey(Post, related_name='comments', on_delete=models.CASCADE)
      name = models.CharField(max_length=100)
      email = models.EmailField()
      body = models.TextField()
      date_added = models.DateTimeField(auto_now_add=True)
  
      class Meta:
          ordering = ['date_added']
  
  
  
  </code></pre>