Python Flask SQLAlchemy Pagination

Question

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:

• http://www.ergo.io/tutorials/better-pagination-in-flask/better-pagination-in-flask/
• https://pythonhosted.org/Flask-paginate/
• sqlalchemy pagination

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.

Answer 1

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>

Answer 2

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.

Answer 3

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 %}