There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "In this book, we use Python 3.7, but all versions above 3.5 should work. We also assume that you've already installed numpy and matplotlib."

A block of code is set as follows:

import gym

# create the environment 
env = gym.make("CartPole-v1")
# reset the environment before starting
env.reset()

# loop 10 times
for i in range(10):
    # take a random action
    env.step(env.action_space.sample())
    # render the game
   env.render()

# close the environment
env.close()

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

$ git clone https://github.com/pybox2d/pybox2d
$ cd pybox2d
$ pip install -e .

Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "In reinforcement learning (RL), the algorithm is called the agent, and it learns from the data provided by an environment."