如何使用少量示例

先决条件

本指南假设您熟悉以下概念

• 提示模板
• 示例选择器
• LLMs
• 向量存储

在本指南中，我们将学习如何创建一个简单的提示模板，该模板在生成时为模型提供示例输入和输出。向 LLM 提供少量此类示例称为 少量示例提示，这是一种简单而有效的方法来指导生成，并在某些情况下显着提高模型性能。

少量示例提示模板可以从一组示例构建，也可以从 示例选择器 类构建，该类负责从定义的集合中选择示例子集。

本指南将介绍使用字符串提示模板进行少量示例提示。有关使用聊天消息为聊天模型进行少量示例提示的指南，请参见此处。

为少量示例创建格式化器

配置一个格式化器，将少量示例格式化为字符串。此格式化器应为 PromptTemplate 对象。

from langchain_core.prompts import PromptTemplate

example_prompt = PromptTemplate.from_template("Question: {question}\n{answer}")

API 参考：PromptTemplate

创建示例集

接下来，我们将创建一个少量示例列表。每个示例都应是一个字典，表示上面定义的格式化器提示的示例输入。

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
""",
    },
]

让我们用我们的一个示例测试格式化提示

print(example_prompt.invoke(examples[0]).to_string())

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

将示例和格式化器传递给 FewShotPromptTemplate

最后，创建一个 FewShotPromptTemplate 对象。此对象接收少量示例和少量示例的格式化器。当格式化此 FewShotPromptTemplate 时，它使用 example_prompt 格式化传递的示例，然后在 suffix 之前将其添加到最终提示中

from langchain_core.prompts import FewShotPromptTemplate

prompt = 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()
)

API 参考：FewShotPromptTemplate

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


Question: 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, 1952


Question: 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 Ball


Question: 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: No


Question: Who was the father of Mary Ball Washington?

通过向模型提供这样的示例，我们可以引导模型获得更好的响应。

使用示例选择器

我们将重用上一节中的示例集和格式化器。但是，我们将示例馈送到 ExampleSelector 的一个实现，称为 SemanticSimilarityExampleSelector 实例，而不是直接将示例馈送到 FewShotPromptTemplate 对象中。此类基于示例与输入的相似性，从初始集中选择少量示例。它使用嵌入模型来计算输入和少量示例之间的相似性，以及向量存储来执行最近邻搜索。

为了展示它的外观，让我们初始化一个实例并在隔离状态下调用它

from langchain_chroma import Chroma
from langchain_core.example_selectors import SemanticSimilarityExampleSelector
from langchain_openai import OpenAIEmbeddings

example_selector = SemanticSimilarityExampleSelector.from_examples(
    # This is the list of examples available to select from.
    examples,
    # This is the embedding class used to produce embeddings which are used to measure semantic similarity.
    OpenAIEmbeddings(),
    # This is the VectorStore class that is used to store the embeddings and do a similarity search over.
    Chroma,
    # This is the number of examples to produce.
    k=1,
)

# Select the most similar example to the input.
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}")

API 参考：SemanticSimilarityExampleSelector | OpenAIEmbeddings

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 Ball

question: Who was the maternal grandfather of George Washington?

现在，让我们创建一个 FewShotPromptTemplate 对象。此对象接收示例选择器和少量示例的格式化器提示。

prompt = FewShotPromptTemplate(
    example_selector=example_selector,
    example_prompt=example_prompt,
    suffix="Question: {input}",
    input_variables=["input"],
)

print(
    prompt.invoke({"input": "Who was the father of Mary Ball Washington?"}).to_string()
)

Question: 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 Ball


Question: Who was the father of Mary Ball Washington?

下一步

您现在已经学习了如何向提示添加少量示例。

接下来，查看本节中关于提示模板的其他操作指南，以及关于 使用聊天模型进行少量示例提示 的相关操作指南，或其他的 示例选择器操作指南。