[Python] How to refresh items on a page without page refresh in Flask

I'm trying to add a script which directs me to the same page with refreshed content.

I'm using an sqlite3 database for my code and when i try it only works with the page refresh. This is one of my SQL structures.

CREATE TABLE classes (
model_id TEXT NOT NULL,
class_number INTEGER,
class_name TEXT,
FOREIGN KEY(model_id) REFERENCES models(model_id)
);


The problem is this is my flask route i use this kind of structure:

@app.route("/model/<model_id>",methods=["POST","GET"])
@login_required
def view_model(model_id):
...
with sqlite3.connect("database.db") as con:
.
.
.
return render_template("train.html",
categories=CATEGORIES,
model_id=model_id,
model=model,
classes=classes,
images=images,
istrained=istrained,
test_image=test_image
)
images=images)


And when ijust need to change the SQL just like in this route i need to either redirect(f"/model/{model_id}") or return "",402.In the first case all the page reloads and since the sql change it successfully reloads all the page.Also when i try the second one nothing applies since the classes is defined in the first route.

@app.route("/add_class/<model_id>",methods=["POST","GET"])
@login_required
def add_class(model_id):
with sqlite3.connect("database.db") as con:
con.row_factory = sqlite3.Row
db = con.cursor()
result = db.execute("SELECT MAX(class_number) FROM classes WHERE model_id = ?", (model_id,)).fetchone()
max_num = result[0] if result and result[0] is not None else 0
default_num = int(max_num +1)
default_name = "Class " + str(max_num + 1)
db.execute("INSERT INTO classes (model_id,class_name,class_number) VALUES(?,?,?)",
(model_id,default_name,default_num))
con.commit()
return redirect(f"/model/{model_id}")


I need to find a way to change the content but without all the page reloading.And want to know are there any ways to solve this problem without javascript.

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