CODEWITHSUNDEEP
pythondjango
MikiBelavista
MikiBelavista

Reputation: 2748

What is request.GET.get doing?

I am looking at A.Mele Django by Example,chapter1

def post_list(request, category=None):
    object_list = Post.published.all()
    paginator = Paginator(object_list, 3) # 3 posts in each page
    page = request.GET.get('page')
    try:
        posts = paginator.page(page)
    except PageNotAnInteger:
        # If page is not an integer deliver the first page
        posts = paginator.page(1)
    except EmptyPage:
        # If page is out of range deliver last page of results
        posts = paginator.page(paginator.num_pages)
    return render(request, 'blog/post/list.html', {'page': page,
                                                   'posts': posts})

This line that gets page is what I really do not understand.

page = request.GET.get('page')

Get method sends user information with the request. But what is get actually doing? This is blog/post/list.html

{% extends "blog/base.html" %}

{% block title  %}My blog{% endblock %}
{% block content %}

  {% include "pagination.html" with page=posts %}

  <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 %}
{% endblock %}

Upvotes: 2

Views: 3530

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 477284

In a URL you can send parameters. For example:

https://www.example.com/some/path/foo.html?key1=val1&key2=val2

The part in boldface contains two parameters: key1 and key2, and the values are val1 and val2 respectively.

The request.GET decodes these parameters and stores it in a QueryDict. This is basically some sort of dictionary (but a key can map to multiple values).

We here thus look for a ?page=1 parameter, and obtain this with request.GET.get('page'). In case no such parameter is given, None is returned.

We can use this for pagination, since a page can for example contain URLs for the next and previous page, where the ?page= parameter, will be incremented or decremented.

The base.html therefore probably contains some logic that generates links with on the second page links to ?page=1 and ?page=3 that thus link to the same URL, but with different parameters. Django then decodes these parameters, and paginates the queryset accordingly.

Usually one encodes parameters in the URL in case the URL has no side-effects (meaning no significant data in the database changes). The advantage of encoding data in the URL is that if you for example share a URL to a friend, he/she will see the same pagination (and therefore the page will not per se display the first blogpost).

This is in contrast to URLs that are for example used to log in or to perform certain effects: then the data is typically encoded in the request headers. As a result you will not share sensitive data to a person with which you share the URL, and making the request a second time typically has no effects.

Upvotes: 10

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