fix(langchain): try/catch langchain import in service; Only langchain is installed with the [langchain] extra (#190)

examples/foundational/07b-interruptible-langchain.py

@@ -36,7 +36,7 @@ try:
 
 except ModuleNotFoundError as e:
     logger.exception(
-        "You need to `pip install langchain langchain-openai langchain-community` for this example. Also, be sure to set `OPENAI_API_KEY` in the environment variable."
+        "In order to run this example you need to `pip install pipecat-ai[langchain] langchain-community langchain-openai. Also, be sure to set `OPENAI_API_KEY` in the environment variable."
     )
     raise Exception(f"Missing module: {e}")
 
@@ -94,12 +94,12 @@ async def main(room_url: str, token):
 
         pipeline = Pipeline(
             [
-                transport.input(),  # Transport user input
-                tma_in,  # User responses
-                lc,  # Langchain
-                tts,  # TTS
-                transport.output(),  # Transport bot output
-                tma_out,  # Assistant spoken responses
+                transport.input(),      # Transport user input
+                tma_in,                 # User responses
+                lc,                     # Langchain
+                tts,                    # TTS
+                transport.output(),     # Transport bot output
+                tma_out,                # Assistant spoken responses
             ]
         )
 

pyproject.toml

@@ -40,7 +40,7 @@ examples = [ "python-dotenv~=1.0.0", "flask~=3.0.3", "flask_cors~=4.0.1" ]
 fal = [ "fal-client~=0.4.0" ]
 google = [ "google-generativeai~=0.5.3" ]
 fireworks = [ "openai~=1.26.0" ]
-langchain = [ "langchain~=0.2.1", "langchain-community~=0.2.1" ]
+langchain = [ "langchain~=0.2.1" ]
 local = [ "pyaudio~=0.2.0" ]
 moondream = [ "einops~=0.8.0", "timm~=0.9.16", "transformers~=4.40.2" ]
 openai = [ "openai~=1.26.0" ]

src/pipecat/services/langchain.py

@@ -1,8 +1,6 @@
 import sys
 from typing import Union
 
-from langchain_core.messages import AIMessageChunk
-from langchain_core.runnables import Runnable
 from loguru import logger
 
 from pipecat.frames.frames import (Frame, LLMFullResponseEndFrame,
@@ -11,6 +9,15 @@ from pipecat.frames.frames import (Frame, LLMFullResponseEndFrame,
                                    TextFrame)
 from pipecat.processors.frame_processor import FrameDirection, FrameProcessor
 
+try:
+    from langchain_core.messages import AIMessageChunk
+    from langchain_core.runnables import Runnable
+except ModuleNotFoundError as e:
+    logger.exception(
+        "In order to use Langchain, you need to `pip install pipecat-ai[langchain]`. "
+    )
+    raise Exception(f"Missing module: {e}")
+
 
 class LangchainProcessor(FrameProcessor):
     def __init__(self, chain: Runnable, transcript_key: str = "input"):