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I am having trouble implementing pagination with Flask-SQLAlchemy or Flask-Pagination, either or. I am unsure how to initialize the pagination, setting pages, determining pages, offest, etc. I am coming from PHP, quite new to Python.

I am querying all the posts in my database

posts = Posts.query.order_by(Posts.time.desc()).all()

I have been looking at the following examples:

I am confused on really what to do, the information I am finding greatly differs between articles. It's left me with confusion and not knowing where to begin. I want to query all rows of the database table, limit the results to 20 and paginate. I'm not seeing this clearly.

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4 Answers 4

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65

I recommend using Flask-SQLAlchemy's pagination: http://flask-sqlalchemy.pocoo.org/2.1/api/?highlight=pagination#flask.ext.sqlalchemy.Pagination

There's a well-written example here: https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-ix-pagination

Here's the basic idea for the view:

@app.route('/myview/<int:page>',methods=['GET'])
def view(page=1):
    per_page = 10
    posts = Posts.query.order_by(Posts.time.desc()).paginate(page,per_page,error_out=False)
    return render_template('view.html',posts=posts)

And then for the template (I don't know your posts model so I made something up):

<html>
  <head>
    Posts
  </head>
  <body>

{% for post in posts.items %}
<p>
  {{ post.post_name }} post body: <b>{{ post.body }}</b>
</p>
{% endfor %}
{% if posts.has_prev %}<a href="{{ url_for('view', page=posts.prev_num) }}">&lt;&lt; Newer posts</a>{% else %}&lt;&lt; Newer posts{% endif %} | 
{% if posts.has_next %}<a href="{{ url_for('view', page=posts.next_num) }}">Older posts &gt;&gt;</a>{% else %}Older posts &gt;&gt;{% endif %}

  </body>
</html>
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7 Comments

Minor change required - @app.route('/myview/', methods=['GET'], defaults={"page": 1}) @app.route('/myview/<int:page>',methods=['GET']) def view(page):
How to accept the sort column name and order (asc/desc) as query parameters? My UI view has controls on each column head to permit sorting on that column, ascending or descending. Makes a big difference for pagination results :)
@chrisinmtown: probably worth it's own question! Or you can just look at the many questions already about this! Here's one: stackoverflow.com/questions/24892035/…
Sorry, poor wording. Should have written "How to pass sort column and order (asc/desc) strings from query parameters to the order_by() method?"
@chrisinmtown: oh, I really don't think that method accepts an argument for that. You can have an if block to handle. For example, if args.sort_order == 'desc': # do something here, and you get the idea.
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6

Controller

@app.route('/', methods=['GET'], defaults={"page": 1}) 
@app.route('/<int:page>', methods=['GET'])
def index(page):
    page = page
    per_page = 2
    users = User.query.paginate(page,per_page,error_out=False)
    # print("Result......", users)
    return render_template("index.html", users=users)

in the View

{% for user in users.items %}
    <h1> {{ user.name }} </h1>
{% endfor %}

<nav aria-label="Page navigation example">
                <ul class="pagination">
                    {% if users.has_prev %}
                      <li class="page-item"> <a class="page-link" href="{{ url_for('index', page=users.prev_num) }}">Previous</a></li>
                    {% else %}
                      <li class="page-item"><a class="page-link btn disabled" href="#">Previous</a></li>
                    {% endif %}


                    {% if users.has_next %}
                      <li class="page-item"> <a class="page-link" href="{{ url_for('index', page=users.next_num) }}">Next</a></li>
                    {% else %}
                      <li class="page-item"><a class="page-link btn disabled" href="#">Next</a></li>
                    {% endif %}

                </ul>
              </nav>
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Comments

3

I used @user3186184 code but I got this error:

TypeError: 'Pagination' object is not iterable

But when I add items to the end of these code:

users = User.query.paginate(page,per_page,error_out=False).items

My issue was fixed.

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Comments

-1

Here is the simplest answer to add pagination in flask

no_of_posts = 3
page = request.args.get("number")
    if page is None:
        page = 1
    else:
        page = int(page)
    allPosts = Posts.query.filter_by().all()
    length = len(allPosts)
    allPosts = allPosts[(page-1)*no_of_posts: page*no_of_posts]
    if page > 1:
        prev = page -1
    else:
        prev = None
    if page < math.ceil(length/no_of_posts):
        next = page + 1
    else:
        next = None

In the template

{% if prev %}
<a href="?number={{ prev }}">&laquo; Previous</a>
{% endif %}
{% if next %}
<a href="?number={{ next }}">Next &raquo;</a>
{% endif %}
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1 Comment

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