Merge pull request #124 from holoviz-topics/langchain_lcel

Langchain lcel

docs/examples/langchain/langchain_streaming_lcel_with_memory.py

@@ -0,0 +1,56 @@
+"""
+Demonstrates how to use the `ChatInterface` to create a chatbot using
+[LangChain Expression Language](https://python.langchain.com/docs/expression_language/) (LCEL)
+with streaming and memory.
+"""
+
+from operator import itemgetter
+
+import panel as pn
+from langchain.memory import ConversationSummaryBufferMemory
+from langchain_core.output_parsers import StrOutputParser
+from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
+from langchain_core.runnables import RunnableLambda, RunnablePassthrough
+from langchain_openai import ChatOpenAI
+
+pn.extension()
+
+SYSTEM_PROMPT = "Try to be a silly comedian."
+
+
+async def callback(contents, user, instance):
+    message = ""
+    inputs = {"input": contents}
+    async for token in chain.astream(inputs):
+        message += token
+        yield message
+    memory.save_context(inputs, {"output": message})
+
+
+model = ChatOpenAI(model="gpt-3.5-turbo")
+memory = ConversationSummaryBufferMemory(return_messages=True, llm=model)
+prompt = ChatPromptTemplate.from_messages(
+    [
+        ("system", SYSTEM_PROMPT),
+        MessagesPlaceholder(variable_name="history"),
+        ("human", "{input}"),
+    ]
+)
+output_parser = StrOutputParser()
+chain = (
+    RunnablePassthrough.assign(
+        history=RunnableLambda(memory.load_memory_variables) | itemgetter("history")
+    )
+    | prompt
+    | model
+    | output_parser
+)
+
+chat_interface = pn.chat.ChatInterface(
+    pn.chat.ChatMessage(
+        "Offer a topic and ChatGPT will try to be funny!", user="System"
+    ),
+    callback=callback,
+    callback_user="ChatGPT",
+)
+chat_interface.servable()

tests/ui/user.py

@@ -175,6 +175,14 @@ def langchain_lcel(page: Page):
     page.wait_for_timeout(5000)
 
 
+def langchain_streaming_lcel_with_memory(page: Page):
+    chat = ChatInterface(page)
+    chat.send("Remember this number: 8. Be concise.")
+    page.wait_for_timeout(10000)
+    chat.send("What number did I just ask you to remember?")
+    page.wait_for_timeout(10000)
+
+
 def mistral_and_llama(page: Page):
     chat = ChatInterface(page)
     chat.send("What do you think about HoloViz in a single sentence?")