Python: Age Calculator using Tkinter

Prerequisites :Introduction to tkinter

Python offers multiple options for developing a GUI (Graphical User Interface). Out of all the GUI methods, Tkinter is the most commonly used method. It is a standard Python interface to the Tk GUI toolkit shipped with Python. Python with Tkinter outputs the fastest and easiest way to create GUI applications. Now, it’s up to the imagination or necessity of a developer, what he/she wants to develop using this toolkit.

To create a Tkinter : 

• Importing the module – Tkinter
• Create the main window (container)
• Add any number of widgets to the main window.
• Apply the event Trigger on the widgets.

The GUI would look like below:

Let’s create a GUI based simple Age Calculator application that can calculate the age with respect to the given date and birth date, given by the user.

Below is the implementation :

Python3

# import all functions from the tkinter
from tkinter import *

# import messagebox class from tkinter
from tkinter import messagebox

# Function for clearing the
# contents of all text entry boxes
def clearAll() :

    # deleting the content from the entry box
    dayField.delete(0, END)
    monthField.delete(0, END)
    yearField.delete(0, END)
    givenDayField.delete(0, END)
    givenMonthField.delete(0, END)
    givenYearField.delete(0, END)
    rsltDayField.delete(0, END)
    rsltMonthField.delete(0, END)
    rsltYearField.delete(0, END)

# function for checking error
def checkError() :

    # if any of the entry field is empty
    # then show an error message and clear
    # all the entries
    if (dayField.get() == "" or monthField.get() == ""
        or yearField.get() == "" or givenDayField.get() == ""
        or givenMonthField.get() == "" or givenYearField.get() == "") :

        # show the error message
        messagebox.showerror("Input Error")

        # clearAll function calling
        clearAll()

        return -1

# function to calculate Age
def calculateAge() :

    # check for error
    value = checkError()

    # if error is occur then return
    if value ==  -1 :
        return

    else :

        # take a value from the respective entry boxes
        # get method returns current text as string
        birth_day = int(dayField.get())
        birth_month = int(monthField.get())
        birth_year = int(yearField.get())

        given_day = int(givenDayField.get())
        given_month = int(givenMonthField.get())
        given_year = int(givenYearField.get())


        # if birth date is greater then given birth_month
        # then donot count this month and add 30 to the date so
        # as to subtract the date and get the remaining days
        month =[31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

        if (birth_day > given_day):
            given_month = given_month - 1
            given_day = given_day + month[birth_month-1]


        # if birth month exceeds given month, then
        # donot count this year and add 12 to the
        # month so that we can subtract and find out
        # the difference
        if (birth_month > given_month):
            given_year = given_year - 1
            given_month = given_month + 12

        # calculate day, month, year
        calculated_day = given_day - birth_day;
        calculated_month = given_month - birth_month;
        calculated_year = given_year - birth_year;

        # calculated day, month, year write back
        # to the respective entry boxes

        # insert method inserting the
        # value in the text entry box.

        rsltDayField.insert(10, str(calculated_day))
        rsltMonthField.insert(10, str(calculated_month))
        rsltYearField.insert(10, str(calculated_year))


# Driver Code
if __name__ == "__main__" :

    # Create a GUI window
    gui = Tk()

    # Set the background colour of GUI window
    gui.configure(background = "light green")

    # set the name of tkinter GUI window
    gui.title("Age Calculator")

     # Set the configuration of GUI window
    gui.geometry("525x260")

    # Create a Date Of Birth : label
    dob = Label(gui, text = "Date Of Birth", bg = "blue")

    # Create a Given Date : label
    givenDate = Label(gui, text = "Given Date", bg = "blue")

    # Create a Day : label
    day = Label(gui, text = "Day", bg = "light green")

    # Create a Month : label
    month = Label(gui, text = "Month", bg = "light green")

    # Create a Year : label
    year = Label(gui, text = "Year", bg = "light green")

    # Create a Given Day : label
    givenDay = Label(gui, text = "Given Day", bg = "light green")

    # Create a Given Month : label
    givenMonth = Label(gui, text = "Given Month", bg = "light green")

    # Create a Given Year : label
    givenYear = Label(gui, text = "Given Year", bg = "light green")

    # Create a Years : label
    rsltYear = Label(gui, text = "Years", bg = "light green")

    # Create a Months : label
    rsltMonth = Label(gui, text = "Months", bg = "light green")

    # Create a Days : label
    rsltDay = Label(gui, text = "Days", bg = "light green")

    # Create a Resultant Age Button and attached to calculateAge function
    resultantAge = Button(gui, text = "Resultant Age", fg = "Black", bg = "Red", command = calculateAge)

    # Create a Clear All Button and attached to clearAll function
    clearAllEntry = Button(gui, text = "Clear All", fg = "Black", bg = "Red", command = clearAll)

    # Create a text entry box for filling or typing the information.
    dayField = Entry(gui)
    monthField = Entry(gui)
    yearField = Entry(gui)

    givenDayField = Entry(gui)
    givenMonthField = Entry(gui)
    givenYearField = Entry(gui)

    rsltYearField = Entry(gui)
    rsltMonthField = Entry(gui)
    rsltDayField = Entry(gui)


    # grid method is used for placing
    # the widgets at respective positions
    # in table like structure .
    dob.grid(row = 0, column = 1)

    day.grid(row = 1, column = 0)
    dayField.grid(row = 1, column = 1)

    month.grid(row = 2, column = 0)
    monthField.grid(row = 2, column = 1)

    year.grid(row = 3, column = 0)
    yearField.grid(row = 3, column = 1)

    givenDate.grid(row = 0, column = 4)

    givenDay.grid(row = 1, column = 3)
    givenDayField.grid(row = 1, column = 4)

    givenMonth.grid(row = 2, column = 3)
    givenMonthField.grid(row = 2, column = 4)

    givenYear.grid(row = 3, column = 3)
    givenYearField.grid(row = 3, column = 4)

    resultantAge.grid(row = 4, column = 2)

    rsltYear.grid(row = 5, column = 2)
    rsltYearField.grid(row = 6, column = 2)

    rsltMonth.grid(row = 7, column = 2)
    rsltMonthField.grid(row = 8, column = 2)

    rsltDay.grid(row = 9, column = 2)
    rsltDayField.grid(row = 10, column = 2)

    clearAllEntry.grid(row = 12, column = 2)

    # Start the GUI
    gui.mainloop()

Output :