AI Agents · Lesson

Interactive REPL-Style Agents

Input loops, history, and multi-turn conversation in terminal agents.

What Is a REPL-Style Agent?

A REPL (Read-Eval-Print Loop) is an interactive terminal session where you type input, get output, and continue. Chat agents in the terminal work exactly this way: the user types a message, the agent responds, and the conversation continues until the user exits.

The Basic REPL Loop

The simplest REPL is a while True loop that reads user input with input(), processes it, and prints the result. The loop runs forever until the user signals exit.

def run_agent_repl():
    print('Agent started. Type /exit to quit.')

    conversation_history = []

    while True:
        user_input = input('You: ').strip()

        if not user_input:
            continue  # ignore empty lines

        if user_input == '/exit':
            print('Goodbye!')
            break

        # Add user message to history
        conversation_history.append({'role': 'user', 'content': user_input})

        # Get agent response (here we use a placeholder)
        agent_reply = f'[Agent reply to: {user_input}]'

        conversation_history.append({'role': 'assistant', 'content': agent_reply})
        print(f'Agent: {agent_reply}')

run_agent_repl()

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