Prerequisite: Tkinter Introduction, lambda function
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. Creating a GUI using Tkinter is an easy task.
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.
Below is what the GUI looks like:
Let’s create a GUI-based simple calculator using the Python Tkinter module, which can perform basic arithmetic operations addition, subtraction, multiplication, and division.
Below is the implementation:
Python3
# Python program to create a simple GUI# calculator using Tkinter# import everything from tkinter modulefrom tkinter import *# globally declare the expression variableexpression = ""# Function to update expression# in the text entry boxdef press(num): # point out the global expression variable global expression # concatenation of string expression = expression + str(num) # update the expression by using set method equation.set(expression)# Function to evaluate the final expressiondef equalpress(): # Try and except statement is used # for handling the errors like zero # division error etc. # Put that code inside the try block # which may generate the error try: global expression # eval function evaluate the expression # and str function convert the result # into string total = str(eval(expression)) equation.set(total) # initialize the expression variable # by empty string expression = "" # if error is generate then handle # by the except block except: equation.set(" error ") expression = ""# Function to clear the contents# of text entry boxdef clear(): global expression expression = "" equation.set("")# Driver codeif __name__ == "__main__": # create a GUI window gui = Tk() # set the background colour of GUI window gui.configure(background="light green") # set the title of GUI window gui.title("Simple Calculator") # set the configuration of GUI window gui.geometry("270x150") # StringVar() is the variable class # we create an instance of this class equation = StringVar() # create the text entry box for # showing the expression . expression_field = Entry(gui, textvariable=equation) # grid method is used for placing # the widgets at respective positions # in table like structure . expression_field.grid(columnspan=4, ipadx=70) # create a Buttons and place at a particular # location inside the root window . # when user press the button, the command or # function affiliated to that button is executed . button1 = Button(gui, text=' 1 ', fg='black', bg='red', command=lambda: press(1), height=1, width=7) button1.grid(row=2, column=0) button2 = Button(gui, text=' 2 ', fg='black', bg='red', command=lambda: press(2), height=1, width=7) button2.grid(row=2, column=1) button3 = Button(gui, text=' 3 ', fg='black', bg='red', command=lambda: press(3), height=1, width=7) button3.grid(row=2, column=2) button4 = Button(gui, text=' 4 ', fg='black', bg='red', command=lambda: press(4), height=1, width=7) button4.grid(row=3, column=0) button5 = Button(gui, text=' 5 ', fg='black', bg='red', command=lambda: press(5), height=1, width=7) button5.grid(row=3, column=1) button6 = Button(gui, text=' 6 ', fg='black', bg='red', command=lambda: press(6), height=1, width=7) button6.grid(row=3, column=2) button7 = Button(gui, text=' 7 ', fg='black', bg='red', command=lambda: press(7), height=1, width=7) button7.grid(row=4, column=0) button8 = Button(gui, text=' 8 ', fg='black', bg='red', command=lambda: press(8), height=1, width=7) button8.grid(row=4, column=1) button9 = Button(gui, text=' 9 ', fg='black', bg='red', command=lambda: press(9), height=1, width=7) button9.grid(row=4, column=2) button0 = Button(gui, text=' 0 ', fg='black', bg='red', command=lambda: press(0), height=1, width=7) button0.grid(row=5, column=0) plus = Button(gui, text=' + ', fg='black', bg='red', command=lambda: press("+"), height=1, width=7) plus.grid(row=2, column=3) minus = Button(gui, text=' - ', fg='black', bg='red', command=lambda: press("-"), height=1, width=7) minus.grid(row=3, column=3) multiply = Button(gui, text=' * ', fg='black', bg='red', command=lambda: press("*"), height=1, width=7) multiply.grid(row=4, column=3) divide = Button(gui, text=' / ', fg='black', bg='red', command=lambda: press("/"), height=1, width=7) divide.grid(row=5, column=3) equal = Button(gui, text=' = ', fg='black', bg='red', command=equalpress, height=1, width=7) equal.grid(row=5, column=2) clear = Button(gui, text='Clear', fg='black', bg='red', command=clear, height=1, width=7) clear.grid(row=5, column='1') Decimal= Button(gui, text='.', fg='black', bg='red', command=lambda: press('.'), height=1, width=7) Decimal.grid(row=6, column=0) # start the GUI gui.mainloop() |
Output :
Code Explanation:
- The code starts by importing the necessary modules.
- The tkinter module provides all the basic functionality for creating graphical user interfaces.
- Next, we create a global variable called expression which will store the result of the calculation.
- We also create two functions to update and evaluate the expression.
- Finally, we write driver code to initialize and manage our GUI window.
- In order to create a simple calculator, we first need to define an expression variable.
- This is done by using the global keyword and assigning it an empty string value ( “” ).
- Next, we create two functions to update and evaluate the expression.
- The press function updates the contents of the text entry box while equalpress evaluates the final result of the calculation.
- We next need to create a table-like structure in which our widgets will be placed.
- We do this by using grid method which takes three arguments: columnspan , ipadx , and rowspan .
- These parameters specify how many columns wide, how many rows high, and how many columns per row respectively should be used in our table layout.
- We set columnspan to 4 , meaning that there will be four columns in our table, iPad width divided by 2 (70), multiplied by 1 for each row in our table (iPad height divided
- The code creates a simple calculator using the Tkinter module.
- First, the code imports everything from the Tkinter module.
- Next, the code creates two global variables: expression and total.
- The press() function is used to update the expression variable in the text entry box.
- The equalpress() function is used to evaluate the final expression.
- Finally, the clear() function is used to clear the contents of the text entry box.
- Next, the driver code is created.
- In this code, if __name__ == “__main__”: is executed which will create a GUI window and set its background color to light green and its title to Simple Calculator.
- Next, the geometry() method is used to set the size of the GUI window (270
- The code starts with a few basic objects: a Button object, which has properties for text, font, background color, and command; and a grid object.
- The first three buttons (button1 through button3) each have their own individual commands associated with them.
- When the user clicks on one of these buttons, the corresponding command is executed.
- For example, when the user clicks on button1, its command is to press the number 1 key.
- Similarly, when the user clicks on button2’s command, it will be to press the number 2 key; and so on.
- Similarly, when the user clicks on button4’s command (to increase the value by 1), its grid row and column values will be set to 3 and 0 respectively.
- And finally when clicking on button5’s command (to decrease the value by 1), its grid row and column values will be set to 2 and 1 respectively.
- The code creates seven buttons, each with its own function.
- When the user presses one of the buttons, the corresponding command is executed.
- The first button, button1, has the function press(1).
- When clicked, this button will execute the code lambda: press(1).
- The second button, button2, has the function press(2), and so on.
- When all seven buttons have been clicked, their functions will be executed in order.
