Python Forum

I want to catch an input error and allow the user to correct it.

It is a pretty common task. Can you post the code that currently reads the user input where you want to catch and correct the error?

(May-30-2024, 09:10 AM)Gribouillis Wrote: [ -> ]It is a pretty common task. Can you post the code that currently reads the user input where you want to catch and correct the error?

The following code takes the user input only as HH:MM otherwise an error occurs and the program stops.
I would like to allow the user to be able to re-enter the input without the program terminating.

import tkinter as tk
from tkinter import ttk
from tkinter.messagebox import showinfo

# root window
root = tk.Tk()
root.geometry("300x200")
root.resizable(False, False)
root.title('Time Clock')

# store StartofWork address and EndofWork
StartofWork = tk.StringVar()
EndofWork = tk.StringVar()


def login_clicked():
    """ callback when the login button clicked
    """
    WorkStart = StartofWork.get()
    tdelta = timediff()
    """
    msg = f'Start of Shift: {StartofWork.get()} and End of Shift: {EndofWork.get()}'
    """
    msg = f'Total Hours: {tdelta}'
    showinfo(
        title='Time Calculated',
        message=msg
    )

from datetime import datetime
def timediff():
  WorkStart = StartofWork.get()
  """StartTime = input("Enter Start Time in HH:MM\n") """
  print("This is WorkStart", WorkStart)
  print("This is EndofWork", EndofWork.get())
  FMT = '%H:%M'
  tdelta = datetime.strptime(EndofWork.get(), FMT) - datetime.strptime(StartofWork.get(), FMT)

  return tdelta
 
 # Sign in frame
signin = ttk.Frame(root)
signin.pack(padx=10, pady=10, fill='x', expand=True)


# StartofWork
StartofWork_label = ttk.Label(signin, text="Clock In:")
StartofWork_label.pack(fill='x', expand=True)

StartofWork_entry = ttk.Entry(signin, textvariable=StartofWork)
StartofWork_entry.pack(fill='x', expand=True)
StartofWork_entry.focus()

# EndofWork
password_label = ttk.Label(signin, text="Clock Out:")
password_label.pack(fill='x', expand=True)

password_entry = ttk.Entry(signin, textvariable=EndofWork)
password_entry.pack(fill='x', expand=True)

# login button
login_button = ttk.Button(signin, text="Calculate Time", command=login_clicked)
login_button.pack(fill='x', expand=True, pady=10)


root.mainloop()

Please post code using the bbtags. Makes it easier to help.

Is this what you are trying for?
Added a try block

import tkinter as tk
from tkinter import ttk
from tkinter.messagebox import showinfo, showerror
from datetime import datetime

# root window
root = tk.Tk()
root.geometry("300x200")
root.resizable(False, False)
root.title('Time Clock')

# store StartofWork address and EndofWork
StartofWork = tk.StringVar()
EndofWork = tk.StringVar()


def login_clicked():
    """ callback when the login button clicked
    """
    WorkStart = StartofWork.get()
    tdelta = timediff()

    if tdelta:
        """
        msg = f'Start of Shift: {StartofWork.get()} and End of Shift: {EndofWork.get()}'
        """
        msg = f'Total Hours: {tdelta}'
        showinfo(
        title='Time Calculated',
        message=msg
        )


def timediff():
    WorkStart = StartofWork.get()
    """StartTime = input("Enter Start Time in HH:MM\n") """
    print("This is WorkStart", WorkStart)
    print("This is EndofWork", EndofWork.get())
    FMT = '%H:%M'
    try:
        tdelta = datetime.strptime(EndofWork.get(), FMT) - datetime.strptime(StartofWork.get(), FMT)
        return tdelta
    except ValueError:
        showerror('Error!', 'Time format is not correct.')

# Sign in frame
signin = ttk.Frame(root)
signin.pack(padx=10, pady=10, fill='x', expand=True)


# StartofWork
StartofWork_label = ttk.Label(signin, text="Clock In:")
StartofWork_label.pack(fill='x', expand=True)

StartofWork_entry = ttk.Entry(signin, textvariable=StartofWork)
StartofWork_entry.pack(fill='x', expand=True)
StartofWork_entry.focus()

# EndofWork
password_label = ttk.Label(signin, text="Clock Out:")
password_label.pack(fill='x', expand=True)

password_entry = ttk.Entry(signin, textvariable=EndofWork)
password_entry.pack(fill='x', expand=True)

# login button
login_button = ttk.Button(signin, text="Calculate Time", command=login_clicked)
login_button.pack(fill='x', expand=True, pady=10)

root.mainloop() 

I took the liberty and rewrote your code a little

import tkinter as tk
from tkinter.messagebox import showerror, showinfo
from datetime import datetime

class Action:
    '''
        Action class handles all data manipulations and validations
    '''
    def calculate(self, start, end):
        '''
            Calculate time difference
        '''
        
        # Set format
        fmt = '%H:%M'

        # Use try block to get the calculations and return total. If we get a ValueError return False
        try:
            tdelta = datetime.strptime(end, fmt) - datetime.strptime(start, fmt)
            return tdelta

        except ValueError:
            return False


class Window:
    '''
        Window class handles the window display and presentation
    '''
    def __init__(self, parent):
        self.parent = parent
        parent.columnconfigure(0, weight=1)
        parent.rowconfigure(0, weight=1)
        parent['padx'] = 4
        parent['pady'] = 4
        parent.geometry('300x170+300+300')
        parent.resizable(False, False)
        parent.title('Time Clock')

        container = tk.Frame(parent)
        container['padx'] = 4
        container['pady'] = 4
        container['highlightbackground'] = '#999999'
        container['highlightcolor'] = '#999999'
        container['highlightthickness'] = 1
        container.grid(column=0, row=0, sticky='news')
        container.grid_columnconfigure(0, weight=1)
        container.grid_columnconfigure(1, weight=3)

        label = tk.Label(container, bg='#fffccc')
        label['text'] = 'Time Clock'
        label['fg'] = 'navy'
        label['font'] = ('verdana', 25, 'bold')
        label.grid(column=0, columnspan=2, row=0, sticky='new')

        label = tk.Label(container, text='Clock In:', anchor='w')
        label.grid(column=0, row=1, sticky='new', padx=1, pady=5)

        label = tk.Label(container, text='Clock out:', anchor='w')
        label.grid(column=0, row=2, sticky='new', padx=1, pady=5)

        self.in_entry = tk.Entry(container)
        self.in_entry.grid(column=1, row=1, sticky='new', padx=1, pady=5)

        self.out_entry = tk.Entry(container)
        self.out_entry.grid(column=1, row=2, sticky='new', padx=1, pady=5)

        self.button = tk.Button(container, text='Calculate', cursor='hand2')
        self.button.grid(column=0, columnspan=2, row=3, sticky='e', padx=1, pady=4)


class Controller:
    '''
        Controller class handles communication between the window and action classes
    '''
    def __init__(self, action, window):
        self.action = action 
        self.window = window

        # Set the command for the window button
        self.window.button['command'] = self.calculate

    def calculate(self):
        '''
            Method for calling the calculation function in action class
        '''

        # Grab the entry fields from window class
        start = self.window.in_entry.get().strip()
        end = self.window.out_entry.get().strip()

        # Set and call the calculate method in action class
        validate = self.action.calculate(start, end)

        # If entries are valid show total hours else show error
        if validate:
            showinfo('Time Calculated', f'Total Hours: {validate}')
        else:
            showerror('Error!', 'Please ensure you are entering the correct time format. Uses 24 hour format. An example would be 14:30 = 2:30 pm')
            

if __name__ == '__main__':
    root = tk.Tk()
    controller = Controller(Action(), Window(root))
    root.mainloop()