In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, and user input are shown as follows: "Using Python, we can create our own classes using the class keyword instead of the def keyword."

A block of code is set as follows:

import tkinter as tk    
win = tk.Tk()           
win.title("Python GUI") 
win.mainloop()          

Any command-line input or output is written as follows:

pip install numpy-1.9.2+mkl-cp36-none-win_amd64.whl

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "Next, we will add functionality to the menu items, for example, closing the main window by clicking the Exit menu item and displaying a Help | About dialog."