main.py

import psycopg2
import json


class Database:
    @staticmethod
    def insert(data):
        insert_data = ''
        insert_data_row = []
        field_order = tuple({key for request in data for key in request.keys()})

        for row in data:
            values = [row.get(key) for key in field_order]
            values = ['NULL' if key is None else key for key in values]
            insert_data_row.append(values)

        for request in insert_data_row:
            insert_data += str('(' + ', '.join([repr(i) for i in request]) + '),').replace('\'NULL\'', 'NULL')
        insert_data = insert_data[:-1]

        request = f'INSERT INTO Feed {field_order} '.replace('\'', '') + f'VALUES {insert_data} ON CONFLICT DO NOTHING;'
        return request

    @staticmethod
    def update(data):
        result = ''
        for row in data:
            field_id = row.get('id')
            cur.execute(f"SELECT * FROM Feed WHERE id = '{field_id}'")
            if cur.fetchall():
                keys = [key for key in row.keys() if key != 'id']
                data = [row.get(key) for key in keys]
                if len(keys) > 1:
                    many_items = ['(', ')']
                else:
                    many_items = ['', '']

                request = 'UPDATE Feed SET {set_keys} = {set_values} WHERE id = {field_id}'.format(
                    set_keys=f'{many_items[0]}' + ', '.join(keys) + f'{many_items[1]}',
                    set_values=f'{many_items[0]}' + ', '.join([repr(i) for i in data]) + f'{many_items[1]}',
                    field_id=f'{repr(field_id)};\n'
                )
                result += request

        return result

    @staticmethod
    def delete(keys):
        for row in keys:
            return f"DELETE FROM Feed WHERE id = '{row}';"

database = Database()


def get_create_statement():
    request = 'CREATE TABLE Feed ('
    structure = scheme.get('fields')
    for row in structure:
        if not row.get('default_value'):
            default = ''
        else:
            default = ''.join(f" DEFAULT {row.get('default_value')}")
        request += f"{row.get('name')} {row.get('type')}{default},"
    request = request[:-1] + ');'
    return request


if __name__ == '__main__':
    conn = psycopg2.connect('postgres://postgres:[email protected]:5432') #connection to database
    cur = conn.cursor()

    with open('./db.json') as f:
        scheme = json.load(f) #reading db structure from file



print(get_create_statement())
print('-------------------------------------------------')
print(database.insert([{"id": '284e4844-be00-45b3-9631-3d05acfc0006', "news_text": 'Hello, world', 'is_read': True},
{"id": '284e4844-be00-45b3-9631-3d05acfc0007'}]))
print('-------------------------------------------------')
print(database.delete(['284e4844-be00-45b3-9631-3d05acfc0006']))
print('-------------------------------------------------')
print(database.update([
{"id": '284e4844-be00-45b3-9631-3d05acfc0006', "news_text": 'Hello, world123', 'is_read': True},
{"id": '284e4844-be00-45b3-9631-3d05acfc0007', "news_text": 'Hello, world123678'},
{"id": '284e4844-be00-45b3-9631-3d05acfc0008', "is_read": 'true'}
]))