Merge pull request #123 from holoviz-topics/langchain_lcel

Add example for Langchain LCEL

docs/examples/langchain/langchain_lcel.py

@@ -0,0 +1,34 @@
+"""
+Demonstrates how to use the `ChatInterface` to create a chatbot using
+[LangChain Expression Language](https://python.langchain.com/docs/expression_language/) (LCEL).
+"""
+
+import panel as pn
+from langchain_core.output_parsers import StrOutputParser
+from langchain_core.prompts import ChatPromptTemplate
+from langchain_core.runnables import RunnablePassthrough
+from langchain_openai import ChatOpenAI
+
+pn.extension()
+
+
+async def callback(contents, user, instance):
+    message = ""
+    async for token in chain.astream(contents):
+        message += token
+        yield message
+
+
+prompt = ChatPromptTemplate.from_template("Tell me a top-notch joke about {topic}")
+model = ChatOpenAI(model="gpt-3.5-turbo")
+output_parser = StrOutputParser()
+chain = {"topic": RunnablePassthrough()} | prompt | model | output_parser
+
+chat_interface = pn.chat.ChatInterface(
+    pn.chat.ChatMessage(
+        "Offer a topic and ChatGPT will respond with a joke!", user="System"
+    ),
+    callback=callback,
+    callback_user="ChatGPT",
+)
+chat_interface.servable()

pyproject.toml

@@ -99,6 +99,7 @@ dependencies = [
     "tabulate",
     "tiktoken",
     "mistralai",
+    "langchain-openai",
 ]
 
 [project.urls]

tests/ui/user.py

@@ -169,6 +169,12 @@ def langchain_pdf_assistant(page: Page):
     page.wait_for_timeout(10000)
 
 
+def langchain_lcel(page: Page):
+    chat = ChatInterface(page)
+    chat.send("Python")
+    page.wait_for_timeout(5000)
+
+
 def mistral_and_llama(page: Page):
     chat = ChatInterface(page)
     chat.send("What do you think about HoloViz in a single sentence?")