Python - GUI Programming - Entry Widget

The Entry widget is a commonly used widget in graphical user interfaces (GUI) that allows users to input text or numerical data into an application. In Python's tkinter library, the Entry widget is a standard Tkinter widget used for this purpose. In this tutorial, we will learn about the Entry widget in Tkinter and how to use it in Python applications.

Creating an Entry widget:

To create an Entry widget in Tkinter, we can use the following syntax:

entry_widget = tk.Entry(parent_widget, options)

Here, tk refers to the Tkinter library, parent_widget is the widget that the entry widget will be placed in, and options are any additional configuration options that we may want to specify.

Let's create an Entry widget in a new Tkinter window:

import tkinter as tk
root = tk.Tk()
entry_widget = tk.Entry(root)
entry_widget.pack()
root.mainloop()

In this example, we first import the tkinter library and create a new Tkinter window using the Tk() method. Then, we create an Entry widget using the Entry() method and add it to the window using the pack() method. Finally, we run the main event loop using the mainloop() method to display the window.

Configuring an Entry widget:

We can configure the appearance and behavior of an Entry widget using various configuration options. Some common options are:

textvariable: Sets or gets the value of the entry widget as a StringVar() variable.

  • show: Specifies a character to be displayed instead of the actual text entered in the entry widget, useful for creating password fields.
  • state: Disables or enables the entry widget, and specifies whether the widget is readonly or not.
  • validate: Specifies when validation should occur, either when the widget loses focus, or during text input.
  • width: Specifies the width of the entry widget in characters.
  • justify: Specifies the horizontal alignment of the text in the entry widget.
  • Example:

Let's add some configuration options to the Entry widget created earlier:

import tkinter as tk
root = tk.Tk()
# create a StringVar variable to hold the entry value
entry_var = tk.StringVar()
# create an Entry widget with some options
entry_widget = tk.Entry(root, textvariable=entry_var, show="*", state="normal", validate="key", width=20, justify="center")
entry_widget.pack()
root.mainloop()

In this example, we create a StringVar() variable to hold the value of the Entry widget. Then, we create the Entry widget with various options such as textvariable to set the value of the widget to entry_var, show to hide the actual text entered and display * instead, state to set the widget to be editable, validate to validate the text during input, width to set the width of the widget, and justify to set the alignment of the text.

Getting and Setting the value of an Entry widget:

To get the value of an Entry widget, we can use the get() method:

entry_value = entry_var.get()

Here, entry_var is the StringVar() variable that we associated with the Entry widget.

To set the value of an Entry widget, we can use the set() method:

entry_var.set("New Value")

Let's create an Entry widget, set its value, and get its value:

import tkinter as tk
root = tk.Tk()
# Create an Entry widget
entry = tk.Entry(root, width=30)
entry.pack()
# Add a button to display the value entered in the Entry widget
def display_value():
    value = entry.get()
    print(f"The value entered is: {value}")
button = tk.Button(root, text="Display Value", command=display_value)
button.pack()
root.mainloop()

In this example, we import the tkinter module and create a Tk object. We then create an Entry widget and add it to the window using the pack geometry manager.

Next, we define a function display_value that retrieves the value entered in the Entry widget using the get method, and prints it to the console. We create a Button widget and assign this function to the command parameter.

Finally, we use the pack geometry manager to add the Button widget to the window, and start the main event loop using the mainloop method of the Tk object.

When the user types a value into the Entry widget and clicks the Display Value button, the value is retrieved using the get method and displayed on the console.