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, dummy URLs, user input, and Twitter handles are shown as follows: "The LCD, controlled by the FrontPanelDisplay class, writes to the serial port, /dev/ttyO4, on BBB's UART 4 at 9600 baud."

A block of code is set as follows:

self.clear_screen()
up_str = '{0:<16}'.format('Up:   ' + self.block_char * up)
dn_str = '{0:<16}'.format('Down: ' + self.block_char * down)

self.port.write(up_str)
self.port.write(dn_str)

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

import Adafruit_BBIO.UART as UART
import serial
class FrontPanelDisplay(object):

  def __init__(self):
    self.uart = 'UART4'
    UART.setup(self.uart)
    self.port = serial.Serial(port="/dev/ttyO4", baudrate=9600)
    self.port.open()

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

Mar 25 21:37:43.000 [notice] Tor has successfully opened a circuit. Looks like client functionality is working.
Mar 25 21:37:43.000 [notice] Bootstrapped 100%: Done.

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: "To connect to your bridge, launch the Tor browser and click on Open Settings as it starts up."