Flask - Query route and object creation - flask

Question

I am quite new to Flask and not sure what would be the proper way to handle that. I am working on a Flask app with a lot of view that retrieves data from MongoDB. I decided to build my own pagination class so I am able to modify the pagination structure based on my view.
I decided to import the Pagination class in one of my views where I am displaying all the customers in a table. The issue I have is my route /clients is handling every GET requests without query parameters (http://127.0.0.1:5000/clients) or with query parameters (http://127.0.0.1:5000/clients?page=3). My pagination object need to know the total number of items in order to be created number_of_items.
Therefore, overtime I am calling the /client route, I am creating a new Pagination object which is not my purpose as I just want to initialize the object on the first time the user reaches /clients and after that I will use my increase(quantity) and decrease(quantity) methods from the Pagination object to change page.
Do you have any idea on where should I avoid to create a Pagination object whenever I am changing page and instead calling methods from the Pagination object (increase and decrease page number)?
customers/views.py
#customers.route('/clients', methods=['GET'])
#login_required
def clients():
""" Client customers list overview page """
page = request.args.get(key='page', default=0)
collection = mongo.db[customers_production]
number_of_items = collection.count()
# just want to create that object once
client_pagination = Pagination(number_of_items, ITEMS_PER_PAGE, 3)
items_to_skip = client_pagination.number_of_previous_items()
cursor = collection.find().skip(items_to_skip).limit(ITEMS_PER_PAGE)
customers = cursor.sort("Last Name", pymongo.ASCENDING)
page_data = client_pagination.dict()
return render_template("clients.html", customers=customers, pagination=page_data)
pagination.py
class Pagination():
def __init__(self, total_items, items_per_page, page_range):
self.total_items = total_items # total number of article to display in total
self.items_per_page = items_per_page # maximum number of article per page
self.page_range = page_range # number of previous and next pages to display
self.current_page = 0
self.number_of_pages = math.ceil(
self.total_items / self.items_per_page)
# if the current_page is 7 and page_range is 3 then self.following will be [8, 9, 10] and self.previous [4, 5 ,6]
self.following = list(
range(self.current_page + 1, self.current_page + self.page_range + 1))
# empty because by default the current page is 0 so no previous
self.previous = list()
def increase(self, quantity):
if self.current_page + quantity > self.number_of_pages:
raise ValueError(
f'The maximum number of pages is {self.number_of_pages}')
else:
self.current_page += quantity
self.following = list()
self.previous = list()
for i in range(1, self.page_range + 1):
new_following_page_number = i + self.current_page
new_previous_page_number = self.current_page - i
self.previous.insert(i, new_previous_page_number)
if new_following_page_number < self.number_of_pages:
self.following.insert(i, new_following_page_number)
def decrease(self, quantity):
if self.current_page - quantity < self.number_of_pages:
raise ValueError(f'The mimimum number of pages is 0')
else:
self.current_page -= quantity
self.following = list()
self.previous = list()
for i in range(1, self.page_range + 1):
new_following_page_number = i + self.current_page
new_previous_page_number = self.current_page - i
self.following.insert(i, new_following_page_number)
if new_previous_page_number > self.number_of_pages:
self.previous.insert(i, new_previous_page_number)
def number_of_previous_items(self):
""" Sum of all items in all previous pages not including the current page """
if self.current_page == 0:
return 0
return self.items_per_page * self.current_page
# method call to display elements on the HTML page
def dict(self):
return {
"current_page": self.current_page,
"next_pages": self.following,
"previous_pages": self.previous,
"number_of_pages": self.number_of_pages
}