example2.py

from sys import stderr
from math import inf

from sqlalchemy.exc import SQLAlchemyError
from values import ValueDatabase, Value

from kivy.app import App
from kivy.properties import NumericProperty


class Example2App(App):
    smallest_positive = NumericProperty(inf)

    @staticmethod
    def _find_smallest_positive(values):
        result = inf
        for value in values:
            if 0 < value < result:
                result = value
        return result

    def on_start(self):
        url = ValueDatabase.construct_mysql_url('localhost', 3306, 'values', 'root', 'cse1208')
        value_database = ValueDatabase(url)
        session = value_database.create_session()
        values = [record.value for record in session.query(Value).all()]
        self.smallest_positive = Example2App._find_smallest_positive(values)


def main():
    try:
        app = Example2App()
        app.run()
    except SQLAlchemyError as exception:
        print('Database connection failed!', file=stderr)
        print(f'Cause: {exception}', file=stderr)
        exit(1)


if __name__ == '__main__':
    main()