Book Image

Deep Reinforcement Learning Hands-On

By : Maxim Lapan
Book Image

Deep Reinforcement Learning Hands-On

By: Maxim Lapan

Overview of this book

Deep Reinforcement Learning Hands-On is a comprehensive guide to the very latest DL tools and their limitations. You will evaluate methods including Cross-entropy and policy gradients, before applying them to real-world environments. Take on both the Atari set of virtual games and family favorites such as Connect4. The book provides an introduction to the basics of RL, giving you the know-how to code intelligent learning agents to take on a formidable array of practical tasks. Discover how to implement Q-learning on 'grid world' environments, teach your agent to buy and trade stocks, and find out how natural language models are driving the boom in chatbots.
Table of Contents (23 chapters)
Deep Reinforcement Learning Hands-On
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The anatomy of the agent

As we saw in the previous chapter, there are several entities in RL's view of the world:

  • Agent: A person or a thing that takes an active role. In practice, it's some piece of code, which implements some policy. Basically, this policy must decide what action is needed at every time step, given our observations.

  • Environment: Some model of the world, which is external to the agent and has the responsibility of providing us with observations and giving us rewards. It changes its state based on our actions.

Let's show how both of them can be implemented in Python for a simplistic situation. We will define an environment that gives the agent random rewards for a limited number of steps, regardless of the agent's actions. This scenario is not very useful, but will allow us to focus on specific methods in both the environment and the agent classes. Let's start with the environment:

class Environment:
    def __init__(self):
        self.steps_left = 10

In the preceding code...