Whenever a user connects to your Chainlit app, a new chat session is created. A chat session goes through a life cycle of events, which you can respond to by defining hooks.

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On Chat Start

The on_chat_start decorator is used to define a hook that is called when a new chat session is created. 
@cl.on_chat_start
def on_chat_start():
    print("A new chat session has started!")

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On Message

The on_message decorator is used to define a hook that is called when a new message is received from the user. 
@cl.on_message
def on_message(msg: cl.Message):
    print("The user sent: ", msg.content)

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On Stop

The on_stop decorator is used to define a hook that is called when the user clicks the stop button while a task was running. 
@cl.on_stop
def on_stop():
    print("The user wants to stop the task!")

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On Chat End

The on_chat_end decorator is used to define a hook that is called when the chat session ends either because the user disconnected or started a new chat session. 
@cl.on_chat_end
def on_chat_end():
    print("The user disconnected!")

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On Chat Resume

The on_chat_resume decorator is used to define a hook that is called when a user resumes a chat session that was previously disconnected. This can only happen if authentication and data persistence are enabled. 
from chainlit.types import ThreadDict

@cl.on_chat_resume
async def on_chat_resume(thread: ThreadDict):
    print("The user resumed a previous chat session!")