langchain-evolution-deck/examples/slide-016/script.py

"""
Slide 16: RunnableLambda + RunnablePassthrough
Section 1: LangChain 1.0
Source: slides/section1-chains/slide-16.js

Сгенерировано автоматически из slide-NN.js / sectionN.pptx.
Паттерн провайдера скопирован из
bro-js/agents/teacher/assistant/src/angry_teacher/llm.py.

Запуск:
  cd langchain-evolution-deck
  cp .env.example .env   # заполни OPENAI_API_KEY
  python examples/slide-016/script.py
"""
import os
from dotenv import load_dotenv
from langchain_openai import ChatOpenAI

load_dotenv()

llm = ChatOpenAI(
    # model="openrouter/free",
    # model="qwen/qwen3.5-35b-a3b",
    model="openai/gpt-oss-20b",
    # model="nvidia/nemotron-3-nano",
    # model="qwen/qwen3.5-9b",
    base_url="https://llm.brojs.ru/v1",
    # base_url="https://api.minimax.io/v1",
    # base_url="http://0.0.0.0:8090/v1",
    # base_url="https://openrouter.ai/api/v1",
    # api_key=os.getenv("MINIMAX_API_KEY"),
    api_key=(os.getenv("OPENAI_API_KEY") or "").strip() or None,
    temperature=0.7,
    stream_usage=True,
)


# === Code from slide 16 ===
from langchain_core.runnables import RunnableLambda, RunnablePassthrough

# RunnableLambda -- оборачивает произвольную функцию
upper = RunnableLambda(lambda x: x.upper())
word_count = RunnableLambda(lambda text: {"text": text, "words": len(text.split())})

# RunnablePassthrough -- пропускает вход дальше (для branching)
passthrough = RunnablePassthrough()

# Пример: текст -> uppercase -> посчитать слова -> смёрджить с оригиналом
chain = (
    word_count
    | RunnablePassthrough.assign(upper=upper)
)

result = chain.invoke("hello world from langchain")
print(result)
# {"text": "hello world from langchain",
#  "words": 4, "upper": "HELLO WORLD FROM LANGCHAIN"}