Quiting while loop through class method

Question


from dataclasses import dataclass, field
from employee import Employee
import json
import re
# from custom_exception import Input_Exception

@dataclass()
class ResourceManager:
    employee_list: dict = field(default_factory=dict)

    def menu(self):
        print('Menu:')
        print('1 : Show data about employee')
        print('2 : Add new employee')
        print('3 : Remove employee')
        print('4 : Add or remove employee hours')
        print('5 : Save changes into the file')
        print('6 : Load data from the file')
        print('7 : Check employee salary')
        print('0 : Exit program')

    def controls(self):
        switch = {
            "1": self.search_employee,
            "2": self.add_employee,
            "3": self.remove_employee,
            "4": self.change_hours,
            "5": self.save_data,
            "6": self.load_data,
            "7": self.check_salary,
            "x": self.quit,
        }

        choice = input("Wybierz jedną opcję:\n=> ")
        if choice in switch.keys():
            switch[choice]()
        else:
            print("Niepoprawny wybór!")


    def quit(self):
        x = False
        return x

ResourceManage is a class used to represent fairly simple CLI, I used dictionary to implement switch and want to use def quit(self) to exit program.

from resource_manager import ResourceManager
if __name__ == '__main__':
    setup = ResourceManager()
    x = True
    while x:
        setup.menu()
        setup.controls()

CLI Menu where I'm trying to use def quit(self) method to quit while loop by changing global x but it dose not work. I've tried quite few different thing but cant get this to work.

How can I fix that?

quit just returns a value; the name of the unnecessary local variable is unrelated to the global variable that controls the loop. — chepner
– chepner, Commented Mar 21, 2022 at 19:42
Nor should quit assume that a global variable named x controls the loop. The loop itself should be incorporated into the class, if anything. — chepner
– chepner, Commented Mar 21, 2022 at 19:43

Stevie · Accepted Answer · 2022-03-21 19:48:25Z

In your code there are two x. One x is in the local function quit, the other is the one in global scope. Assigning one won't change the other.

I would suggest you to add a attribute to the ResourceManager that states whether the cli should exit.

This could work like that:


from dataclasses import dataclass, field
from employee import Employee
import json
import re
# from custom_exception import Input_Exception

@dataclass()
class ResourceManager:
    employee_list: dict = field(default_factory=dict)
    x: bool = True

    def menu(self):
        print('Menu:')
        print('1 : Show data about employee')
        print('2 : Add new employee')
        print('3 : Remove employee')
        print('4 : Add or remove employee hours')
        print('5 : Save changes into the file')
        print('6 : Load data from the file')
        print('7 : Check employee salary')
        print('0 : Exit program')

    def controls(self):
        switch = {
            "1": self.search_employee,
            "2": self.add_employee,
            "3": self.remove_employee,
            "4": self.change_hours,
            "5": self.save_data,
            "6": self.load_data,
            "7": self.check_salary,
            "x": self.quit,
        }

        choice = input("Wybierz jedną opcję:\n=> ")
        if choice in switch.keys():
            switch[choice]()
        else:
            print("Niepoprawny wybór!")


    def quit(self):
        self.x = False
        return self.x

The main can now reference the attribute the following:

if __name__ == '__main__':
    setup = ResourceManager()
    while setup.x:
        setup.menu()
        setup.controls()

I hope i could help you?

Thx for that I never thought about solving this that way. Many thanks.

Jason Jenkins · Accepted Answer · 2022-03-21 19:53:58Z

1

The x that is assigned True in your quit() function is creating a new local variable that is only visible inside the function. You need to use the global keyword to access or mutate the global variable x from inside your function. Also, note that returning the value of x has no effect since the call inside control() doesn't use the value.

    def quit(self):
        global x 
        x = False

Using a global variable like this is generally an anti-pattern though, so you should consider changing x to be a property of your class and checking it in the main loop.

answered Mar 21, 2022 at 19:53

Jason Jenkins

5,4823 gold badges26 silver badges29 bronze badges

1 Comment

Lynx Over a year ago

Thx, it is possible to fix this that way but as you said it is considered anti-pattern. Thank you for your time and help Jason.

Collectives™ on Stack Overflow

Quiting while loop through class method

2 Answers 2

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related