How to compare single Dates with Flask, SQLAlchemy, SQLite

Question

I'm just join the stackoverflow community right now because I trying to complete my first Python-flask application and I got some problem to fetch and compare a single date for single user with sqlalchemy & sqlite.

Here my imports:

from flask import Flask, request, jsonify, render_template, url_for, redirect, flash
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import create_engine, MetaData, func
import datetime

Here my table database model:

class BloodDonation(db.Model):
   id = db.Column(db.Integer, primary_key = True)
   name = db.Column(db.String, nullable=False)
   age = db.Column(db.Integer, nullable=False)
   blood_groups = db.Column(db.String, nullable=False)
   city = db.Column(db.String, nullable=False)
   phone_no = db.Column(db.String, nullable=False)
   latest_donation = db.Column(db.Date, nullable=False)
   next_donation = db.Column(db.Date)
   donation_counter = db.Column(db.Integer, default=1)

This is a easy CRUD application where I should store blood donations inside a database with 3 months threshold donation per user. To do that I use the mobile number as user identifier and I use datetime module, so when an user try to do more than an donation before 90 days the application have to show the message donation forbidden.

Here my code:

@app.route('/blood_donation', methods=['GET','POST'])
def blood_donation():
     if request.method == 'GET':
        blood_groups = ['A+', 'A-', 'B+', 'B-', 'AB+', 'AB-', 'O+', 'O-']
        return render_template('donate.html', blood_groups = blood_groups)

     else:
    donation_day = datetime.date.today()
    next_donation_date = threshold_time(donation_day) # this func return donation date + 90 days
    
    data_fields = ['name','age','blood_groups','city','phone_no']

    data_dict = {}
    data_dict['latest_donation'] = donation_day
    data_dict['next_donation'] = next_donation_date
                  

    for field in data_fields:
        data_dict[field] = request.form.get(field).lower()

    for value in data_dict.values():
       if value == "":
            return "Please enter all the details." 
              
    counter = db.session.query(BloodDonation).filter(BloodDonation.phone_no == data_dict['phone_no']).count() 
    next_bd_date = db.session.query(BloodDonation).filter(func.DATE(BloodDonation.latest_donation) >= 0)
                
    if counter >= 0 and next_bd_date and\
    db.session.query(BloodDonation).filter(func.DATE(BloodDonation.latest_donation)\ 
    <= data_dict['latest_donation']):
       counter += 1
       data_dict['donation_counter'] = counter
       blood_donation = BloodDonation(**data_dict)
       db.session.add(blood_donation)
       db.session.commit()
       return redirect(url_for('home'))   

    return "Donation forbidden!!!"

I think the problem is in the if statement to compare dates and mobile number that I use as donation counter and user identifier since the application continue update the database without return donation forbidden.

Here the wrong code:

    if counter >= 0 and next_bd_date and \
        db.session.query(BloodDonation).filter(func.DATE(BloodDonation.latest_donation) <= 
        data_dict['latest_donation']):

I hope somebody can help me since I am not a pro but a beginner

Thanks in advance!

well get the last donated date and current date and find difference in days, more that 90 then allow else forbid, or create a dummy coloumn which keep the date upto which cant do donation and check if donation trying date is less then that or not — sahasrara62, Oct 28 '20 at 19:20
I tried to do the difference between last donation day and current date but I got this error: TypeError: unsupported operand type(s) for -: 'BloodDonation' and 'datetime.date' — Hamundo, Oct 29 '20 at 11:25
However I need to get a single latest donation date for single user and not a keys values pair list — Hamundo, Oct 29 '20 at 11:31
https://stackoverflow.com/questions/151199/how-to-calculate-number-of-days-between-two-given-dates this may help the no of days, you can use datetime.datetime.utcnow for current date — sahasrara62, Oct 29 '20 at 11:33

score 0 · Answer 1 · answered Oct 28 '20 at 20:13

It looks like you might have several spacing issues. Python doesn't like it if you don't have proper spacing. Try this. Also I wasn't sure where you wanted that final return statement so I'm not sure if I spaced it correctly.

@app.route('/blood_donation', methods=['GET','POST'])
def blood_donation():
    if request.method == 'GET':
        blood_groups = ['A+', 'A-', 'B+', 'B-', 'AB+', 'AB-', 'O+', 'O-']
        return render_template('donate.html', blood_groups = blood_groups)

    else:
        donation_day = datetime.date.today()
        next_donation_date = threshold_time(donation_day)
        
        data_fields = ['name','age','blood_groups','city','phone_no']

        data_dict = {}
        data_dict['latest_donation'] = donation_day
        data_dict['next_donation'] = next_donation_date
                    

        for field in data_fields:
            data_dict[field] = request.form.get(field).lower()

        for value in data_dict.values():
            if value == "":
                return "Please enter all the details." 
                
        counter = db.session.query(BloodDonation).filter(BloodDonation.phone_no == data_dict['phone_no']).count() 
        next_bd = db.session.query(BloodDonation).filter(func.DATE(BloodDonation.latest_donation) >= 0)
                    

        if counter >= 0 and next_bd and \
            db.session.query(BloodDonation).filter(func.DATE(BloodDonation.latest_donation) <= data_dict['latest_donation']):
                counter += 1
                data_dict['donation_counter'] = counter

                blood_donation = BloodDonation(**data_dict)
                db.session.add(blood_donation)
                db.session.commit()
                
                return redirect(url_for('home'))   

        return "Donation forbidden!!!"

it is finding the difference between no of days from last donation to present one if less than 90 then no donation or if more than 90 eligible for donation — sahasrara62, Oct 29 '20 at 11:34
TypeError: unsupported operand type(s) for -: 'BaseQuery' and 'datetime.date' — Hamundo, Oct 29 '20 at 17:39
I got that error because I'm trying to store and fetch next_donation date from my database with this statement : `next_bd_date = db.session.query(BloodDonation).filter(func.DATE(BloodDonation.latest_donation) >= 0)` — Hamundo, Oct 29 '20 at 18:07

How to compare single Dates with Flask, SQLAlchemy, SQLite

1 Answers1