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本教程将介绍如何使用 LangChain 库中的 PromptTemplate 和 FewShotPromptTemplate 来构建和运行提示（prompt），并通过示例数据展示其应用。
安装依赖
首先，确保你已经安装了 langchain 和相关依赖：
pip install langchain langchain_core langchain_chroma langchain_community
1. 创建 PromptTemplate
PromptTemplate 用于定义一个模板，该模板可以动态地插入变量。
代码示例
from langchain_core.prompts import PromptTemplateexample_prompt = PromptTemplate.from_template("Question: {question}\n{answer}")
解释
PromptTemplate.from_template方法用于从给定的模板字符串创建一个PromptTemplate对象。- 模板字符串中的
{question}和{answer}是占位符，将在后续被实际数据替换。
2. 定义示例数据
示例数据是一个列表，每个元素是一个包含 question 和 answer 的字典。
代码示例
examples = [{"question": "Who lived longer, Muhammad Ali or Alan Turing?","answer": """
Are follow up questions needed here: Yes.
Follow up: How old was Muhammad Ali when he died?
Intermediate answer: Muhammad Ali was 74 years old when he died.
Follow up: How old was Alan Turing when he died?
Intermediate answer: Alan Turing was 41 years old when he died.
So the final answer is: Muhammad Ali
""",},{"question": "When was the founder of craigslist born?","answer": """
Are follow up questions needed here: Yes.
Follow up: Who was the founder of craigslist?
Intermediate answer: Craigslist was founded by Craig Newmark.
Follow up: When was Craig Newmark born?
Intermediate answer: Craig Newmark was born on December 6, 1952.
So the final answer is: December 6, 1952
""",},{"question": "Who was the maternal grandfather of George Washington?","answer": """
Are follow up questions needed here: Yes.
Follow up: Who was the mother of George Washington?
Intermediate answer: The mother of George Washington was Mary Ball Washington.
Follow up: Who was the father of Mary Ball Washington?
Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
So the final answer is: Joseph Ball
""",},{"question": "Are both the directors of Jaws and Casino Royale from the same country?","answer": """
Are follow up questions needed here: Yes.
Follow up: Who is the director of Jaws?
Intermediate Answer: The director of Jaws is Steven Spielberg.
Follow up: Where is Steven Spielberg from?
Intermediate Answer: The United States.
Follow up: Who is the director of Casino Royale?
Intermediate Answer: The director of Casino Royale is Martin Campbell.
Follow up: Where is Martin Campbell from?
Intermediate Answer: New Zealand.
So the final answer is: No
""",},
]
解释
- 每个字典包含一个问题和对应的答案。
- 答案部分详细描述了求解问题的中间步骤和最终答案。
3. 使用 PromptTemplate 调用示例
代码示例
print(example_prompt.invoke(examples[0]).to_string())
输出
Question: Who lived longer, Muhammad Ali or Alan Turing?Are follow up questions needed here: Yes.
Follow up: How old was Muhammad Ali when he died?
Intermediate answer: Muhammad Ali was 74 years old when he died.
Follow up: How old was Alan Turing when he died?
Intermediate answer: Alan Turing was 41 years old when he died.
So the final answer is: Muhammad Ali
解释
example_prompt.invoke(examples[0])方法将示例数据中的第一个元素插入到模板中。to_string()方法将结果转换为字符串形式。
4. 创建 FewShotPromptTemplate
FewShotPromptTemplate 用于结合多个示例和一个后缀模板来生成最终的提示。
代码示例
from langchain_core.prompts import FewShotPromptTemplateprompt = FewShotPromptTemplate(examples=examples,example_prompt=example_prompt,suffix="Question: {input}",input_variables=["input"],
)print(prompt.invoke({"input": "Who was the father of Mary Ball Washington?"}).to_string()
)
输出
Question: Who lived longer, Muhammad Ali or Alan Turing?Are follow up questions needed here: Yes.
Follow up: How old was Muhammad Ali when he died?
Intermediate answer: Muhammad Ali was 74 years old when he died.
Follow up: How old was Alan Turing when he died?
Intermediate answer: Alan Turing was 41 years old when he died.
So the final answer is: Muhammad AliQuestion: When was the founder of craigslist born?Are follow up questions needed here: Yes.
Follow up: Who was the founder of craigslist?
Intermediate answer: Craigslist was founded by Craig Newmark.
Follow up: When was Craig Newmark born?
Intermediate answer: Craig Newmark was born on December 6, 1952.
So the final answer is: December 6, 1952Question: Who was the maternal grandfather of George Washington?Are follow up questions needed here: Yes.
Follow up: Who was the mother of George Washington?
Intermediate answer: The mother of George Washington was Mary Ball Washington.
Follow up: Who was the father of Mary Ball Washington?
Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
So the final answer is: Joseph BallQuestion: Are both the directors of Jaws and Casino Royale from the same country?Are follow up questions needed here: Yes.
Follow up: Who is the director of Jaws?
Intermediate Answer: The director of Jaws is Steven Spielberg.
Follow up: Where is Steven Spielberg from?
Intermediate Answer: The United States.
Follow up: Who is the director of Casino Royale?
Intermediate Answer: The director of Casino Royale is Martin Campbell.
Follow up: Where is Martin Campbell from?
Intermediate Answer: New Zealand.
So the final answer is: NoQuestion: Who was the father of Mary Ball Washington?
解释
FewShotPromptTemplate结合了多个示例和一个后缀模板。examples参数是之前定义的示例数据。example_prompt是之前创建的PromptTemplate。suffix是一个后缀模板，用于添加到所有示例之后。input_variables定义了后缀模板中使用的变量。
5. 使用语义相似度选择示例
SemanticSimilarityExampleSelector 用于根据输入问题的语义相似度选择最相关的示例。
代码示例
from langchain_chroma import Chroma
from langchain_core.example_selectors import SemanticSimilarityExampleSelector
from langchain_community.embeddings import ZhipuAIEmbeddingsembed = ZhipuAIEmbeddings(model="embedding-3",api_key="your api key",
)example_selector = SemanticSimilarityExampleSelector.from_examples(examples,embed,Chroma,k=1,
)question = "Who was the father of Mary Ball Washington?"
selected_examples = example_selector.select_examples({"question": question})
print(f"Examples most similar to the input: {question}")
for example in selected_examples:print("\n")for k, v in example.items():print(f"{k}: {v}")
输出
Examples most similar to the input: Who was the father of Mary Ball Washington?answer:
Are follow up questions needed here: Yes.
Follow up: Who was the mother of George Washington?
Intermediate answer: The mother of George Washington was Mary Ball Washington.
Follow up: Who was the father of Mary Ball Washington?
Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
So the final answer is: Joseph Ballquestion: Who was the maternal grandfather of George Washington?
解释
ZhipuAIEmbeddings用于生成问题的嵌入向量。SemanticSimilarityExampleSelector.from_examples创建一个示例选择器，用于根据语义相似度选择示例。k=1表示选择最相似的一个示例。select_examples方法根据输入问题选择最相似的示例。
总结
本教程展示了如何使用 LangChain 中的 PromptTemplate 和 FewShotPromptTemplate 来构建和运行提示，并通过语义相似度选择最相关的示例。这些工具在构建复杂的提示和生成高质量回答方面非常有用。希望这个教程对你有所帮助！
参考链接：https://python.langchain.com/v0.2/docs/how_to/few_shot_examples/
希望这个教程对你有所帮助！如果有任何问题，欢迎随时提问。