3/21 從日本旅行回來後感覺有很多東西要學, 但卻不知從哪一個著手. 昨天整理書桌看到案上的 LangChain 書籍, 想說那就從 LangChain 開始吧! 記得 LangChain 就是去年九月第一次關西之旅回來後開始學習的.
由於我的 LG Gram 筆電的 Thonny Python 執行環境太亂了, 存在嚴重的版本衝突問題, 所以在重新出發之前, 先建立一個專門用來串接 GenAI 的乾淨虛擬環境較好. 我之前曾使用 poetry 來建立與管理虛擬環境, 但本篇則是要使用傳統且熟悉的 venv.
本系列全部測試文章參考 :
開啟命令提示字元視窗建立一個名為 myvenv 虛擬環境 :
D:\python\test>python -m venv myvenv
D:\python\test>myvenv\Scripts\activate
(myvenv) D:\python\test>
用 pip list 檢視可知只有一個 pip 套件而已 :
(myvenv) D:\python\test>pip list
Package Version
------- -------
pip 23.2.1
[notice] A new release of pip is available: 23.2.1 -> 26.0.1
[notice] To update, run: python.exe -m pip install --upgrade pip
更新 pip 版本 :
(myvenv) D:\python\test>python.exe -m pip install --upgrade pip
Requirement already satisfied: pip in d:\python\test\myvenv\lib\site-packages (23.2.1)
Collecting pip
Obtaining dependency information for pip from https://files.pythonhosted.org/packages/de/f0/c81e05b613866b76d2d1066490adf1a3dbc4ee9d9c839961c3fc8a6997af/pip-26.0.1-py3-none-any.whl.metadata
Downloading pip-26.0.1-py3-none-any.whl.metadata (4.7 kB)
Downloading pip-26.0.1-py3-none-any.whl (1.8 MB)
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Installing collected packages: pip
Attempting uninstall: pip
Found existing installation: pip 23.2.1
Uninstalling pip-23.2.1:
Successfully uninstalled pip-23.2.1
Successfully installed pip-26.0.1
(myvenv) D:\python\test>
用下列指令來安裝透過 LangChain 串接 Gemini 與 OpenAI 所需的套件 :
pip install langchain-google-genai langchain-openai python-dotenv
其中 langchain-google-genai 與 langchain-openai 分別是串接 Gemini 與 OpenAI 的外掛, 安裝它們時會自動安裝 LangChain 的核心引擎 langchain-core, 這是 LangChain 的心臟, 包含所有的基礎邏輯 (Base Message, Chat Prompt 等), 安裝外掛時會自動附帶. 注意, 不需要安裝 langchain 套件, 這是一個塞滿了各種實驗性功能和舊代碼的大禮包, 非常龐雜.
(myvenv) D:\python\test>pip install langchain-google-genai langchain-openai python-dotenv
Collecting langchain-google-genai
Downloading langchain_google_genai-4.2.1-py3-none-any.whl.metadata (2.7 kB)
Collecting langchain-openai
Downloading langchain_openai-1.1.12-py3-none-any.whl.metadata (3.1 kB)
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Downloading python_dotenv-1.2.2-py3-none-any.whl.metadata (27 kB)
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Using cached filetype-1.2.0-py2.py3-none-any.whl.metadata (6.5 kB)
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Using cached google_genai-1.70.0-py3-none-any.whl.metadata (52 kB)
Collecting langchain-core<2.0.0,>=1.2.5 (from langchain-google-genai)
Downloading langchain_core-1.2.26-py3-none-any.whl.metadata (4.4 kB)
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Collecting requests<3.0.0,>=2.28.1 (from google-genai<2.0.0,>=1.56.0->langchain-google-genai)
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Collecting openai<3.0.0,>=2.26.0 (from langchain-openai)
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Installing collected packages: filetype, zstandard, xxhash, websockets, uuid-utils, urllib3, typing-extensions, tenacity, sniffio, regex, pyyaml, python-dotenv, pycparser, pyasn1, packaging, orjson, jsonpointer, jiter, idna, h11, distro, colorama, charset_normalizer, certifi, annotated-types, typing-inspection, tqdm, requests, pydantic-core, pyasn1-modules, jsonpatch, httpcore, cffi, anyio, tiktoken, requests-toolbelt, pydantic, httpx, cryptography, openai, langsmith, google-auth, langchain-core, langchain-openai, google-genai, langchain-google-genai
Successfully installed annotated-types-0.7.0 anyio-4.13.0 certifi-2026.2.25 cffi-2.0.0 charset_normalizer-3.4.7 colorama-0.4.6 cryptography-46.0.6 distro-1.9.0 filetype-1.2.0 google-auth-2.49.1 google-genai-1.70.0 h11-0.16.0 httpcore-1.0.9 httpx-0.28.1 idna-3.11 jiter-0.13.0 jsonpatch-1.33 jsonpointer-3.1.1 langchain-core-1.2.26 langchain-google-genai-4.2.1 langchain-openai-1.1.12 langsmith-0.7.25 openai-2.30.0 orjson-3.11.8 packaging-26.0 pyasn1-0.6.3 pyasn1-modules-0.4.2 pycparser-3.0 pydantic-2.12.5 pydantic-core-2.41.5 python-dotenv-1.2.2 pyyaml-6.0.3 regex-2026.4.4 requests-2.33.1 requests-toolbelt-1.0.0 sniffio-1.3.1 tenacity-9.1.4 tiktoken-0.12.0 tqdm-4.67.3 typing-extensions-4.15.0 typing-inspection-0.4.2 urllib3-2.6.3 uuid-utils-0.14.1 websockets-16.0 xxhash-3.6.0 zstandard-0.25.0
檢視目前 pip 套件 :
(myvenv) D:\python\test>pip list
Package Version
---------------------- ---------
annotated-types 0.7.0
anyio 4.13.0
certifi 2026.2.25
cffi 2.0.0
charset-normalizer 3.4.7
colorama 0.4.6
cryptography 46.0.6
distro 1.9.0
filetype 1.2.0
google-auth 2.49.1
google-genai 1.70.0
h11 0.16.0
httpcore 1.0.9
httpx 0.28.1
idna 3.11
jiter 0.13.0
jsonpatch 1.33
jsonpointer 3.1.1
langchain-core 1.2.26
langchain-google-genai 4.2.1
langchain-openai 1.1.12
langsmith 0.7.25
openai 2.30.0
orjson 3.11.8
packaging 26.0
pip 26.0.1
pyasn1 0.6.3
pyasn1_modules 0.4.2
pycparser 3.0
pydantic 2.12.5
pydantic_core 2.41.5
python-dotenv 1.2.2
PyYAML 6.0.3
regex 2026.4.4
requests 2.33.1
requests-toolbelt 1.0.0
sniffio 1.3.1
tenacity 9.1.4
tiktoken 0.12.0
tqdm 4.67.3
typing_extensions 4.15.0
typing-inspection 0.4.2
urllib3 2.6.3
uuid_utils 0.14.1
websockets 16.0
xxhash 3.6.0
zstandard 0.25.0
可見除了核心套件 langchain-core 外, 還有串接 OpenAI 與 Gemini 的 langchain-openai 與 langchain-google-genai 套件; 此外還會安裝底層的 SDK 依賴套件 google-genai 與 openai. 如果想用原生 SDK 串接 API 就可以使用這兩個套件. 其中 google-genai 是谷歌 2024 年底發布的新版 SDK, 用來取代舊版的 google-generativeai (已於 2025 年進入維護模式), 用法參考下面這篇的補充說明 :
先來串接 OpenAI API :
(myvenv) D:\python\test>python
Python 3.12.1 (tags/v3.12.1:2305ca5, Dec 7 2023, 22:03:25) [MSC v.1937 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from dotenv import dotenv_values
>>> config=dotenv_values('.env')
>>> openai_api_key=config.get('OPENAI_API')
>>> from langchain_openai import ChatOpenAI
>>> chat_model=ChatOpenAI(api_key=openai_api_key, model='gpt-3.5-turbo')
>>> response=chat_model.invoke('你是誰?')
>>> response.content
'我是一個機器人助手，可以回答你的問題和提供幫助。有什麼我可以為你做的嗎？'
更換為 gpt-4o-mini 模型 :
>>> chat_model=ChatOpenAI(api_key=openai_api_key, model='gpt-4o-mini')
>>> response=chat_model.invoke('你是誰?')
>>> response.content
'我是一个人工智能助手，旨在回答你的问题和提供帮助。如果你有任何疑问或需要的信息，请随时告诉我！'
下面是串接 Gemini :
>>> from dotenv import dotenv_values
>>> config=dotenv_values('.env')
>>> gemini_api_key=config.get('GEMINI_API_KEY')
>>> from langchain_google_genai import ChatGoogleGenerativeAI
>>> chat_model=ChatGoogleGenerativeAI(api_key=gemini_api_key, model='gemini-2.5-flash')
>>> response=chat_model.invoke('你是誰?')
>>> response.content
'我是一个大型语言模型，由 Google 训练。'
更換模型 :
>>> chat_model=ChatGoogleGenerativeAI(api_key=gemini_api_key, model='gemini-2.5-flash-lite')
>>> response=chat_model.invoke('你是誰?')
>>> response.content
'我是一個大型語言模型，由 Google 訓練。'
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