自然语言处理从入门到应用——LangChain：提示（Prompts）-[提示模板：创建自定义提示模板和含有Few-Shot示例的提示模板]

分类目录：《自然语言处理从入门到应用》总目录

创建自定义提示模板

假设我们希望LLM根据函数名称生成该函数的英文语言解释。为了实现这个任务，我们将创建一个自定义的提示模板，以函数名称作为输入，并格式化提示模板以提供函数的源代码。LangChain提供了一组默认的提示模板，可用于生成各种任务的提示。但是，在某些情况下，默认的提示模板可能无法满足我们的需求。例如，我们可能希望创建一个具有特定动态指令的提示模板，以适应我们的语言模型。在这种情况下，我们可以创建自定义的提示模板。

有两种不同的提示模板：

字符串提示模板：提供一个简单的字符串格式提示
聊天提示模板：生成一个更结构化的聊天API使用的提示

在本文中，我们将使用字符串提示模板创建一个自定义提示。要创建自定义字符串提示模板，有两个要求：

它具有input_variables属性，用于公开提示模板期望的输入变量
它公开一个format方法，该方法接受与预期的input_variables相对应的关键字参数，并返回格式化的提示

我们将创建一个自定义的提示模板，它以函数名称作为输入，并格式化提示以提供函数的源代码。为了实现这一点，让我们首先创建一个函数，该函数将根据函数名称返回函数的源代码。

import inspectdef get_source_code(function_name):# Get the source code of the functionreturn inspect.getsource(function_name)

接下来，我们将创建一个自定义的提示模板，该模板以函数名称作为输入，并格式化提示模板以提供函数的源代码：

from langchain.prompts import StringPromptTemplate
from pydantic import BaseModel, validatorclass FunctionExplainerPromptTemplate(StringPromptTemplate, BaseModel):"""一个自定义的提示模板，接受函数名作为输入，并格式化提示模板以提供函数的源代码。"""@validator("input_variables")def validate_input_variables(cls, v):"""验证输入变量的正确性。"""if len(v) != 1 or "function_name" not in v:raise ValueError("function_name必须是唯一的输入变量。")return vdef format(self, **kwargs) -> str:# 获取函数的源代码source_code = get_source_code(kwargs["function_name"])# 生成要发送给语言模型的提示prompt = f"""给定函数名和源代码，生成一个关于函数的英文语言解释。函数名：{kwargs["function_name"].__name__}源代码：{source_code}解释："""return promptdef _prompt_type(self):return "function-explainer"

现在我们已经创建了一个自定义的提示模板，我们可以使用它来生成我们任务的提示：

fn_explainer = FunctionExplainerPromptTemplate(input_variables=["function_name"])# 为函数"get_source_code"生成一个提示
prompt = fn_explainer.format(function_name=get_source_code)
print(prompt)

输出：

给定函数名和源代码，生成一个关于函数的英文语言解释。
函数名：get_source_code
源代码：
def get_source_code(function_name):# Get the source code of the functionreturn inspect.getsource(function_name)解释：

创建含有Few-Shot示例的提示模板

在下文中，我们将学习如何创建含有Few-Shot示例的提示模板。我们将使用FewShotPromptTemplate类来创建一个含有Few-Shot示例的提示模板。该类可以接受一组示例或者一个ExampleSelector对象。在下文中，我们将分别为自我提问与搜索配置Few-Shot示例讨论这两种选项。

使用示例集

首先，创建一个Few-Shot示例的列表。每个示例应该是一个字典，其中键是输入变量，值是这些输入变量的值。

from langchain.prompts.few_shot import FewShotPromptTemplate
from langchain.prompts.prompt import PromptTemplateexamples = [{"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
"""}
]

然后，我们可以为Few Shot示例创建格式化程序。配置一个将Few Shot示例格式化为字符串的格式化程序。该格式化程序应该是一个PromptTemplate对象。

example_prompt = PromptTemplate(input_variables=["question", "answer"], template="Question: {question}\n{answer}")print(example_prompt.format(**examples[0]))
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

最后，创建一个FewShotPromptTemplate对象。该对象接受Few Shot示例和Few Shot示例的格式化程序作为输入。

prompt = FewShotPromptTemplate(examples=examples, example_prompt=example_prompt, suffix="Question: {input}", input_variables=["input"]
)print(prompt.format(input="Who was the father of Mary Ball Washington?"))

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?

使用示例选择器

我们将重复使用上文中的示例集和格式化程序。但是，与其直接将示例输入到FewShotPromptTemplate对象中，我们将把它们输入到一个ExampleSelector对象中。在下文中，我们将使用SemanticSimilarityExampleSelector类。该类根据示例与输入之间的相似度选择Few-Shot示例。它使用嵌入模型计算输入与Few-Shot示例之间的相似度，并使用向量存储执行最近邻搜索。

from langchain.prompts.example_selector import SemanticSimilarityExampleSelector
from langchain.vectorstores import Chroma
from langchain.embeddings import OpenAIEmbeddingsexample_selector = SemanticSimilarityExampleSelector.from_examples(# 这是可供选择的示例列表。examples,# 这是用于生成嵌入的嵌入类，用于衡量语义相似度。OpenAIEmbeddings(),# 这是用于存储嵌入并进行相似度搜索的向量存储类。Chroma,# 这是要生成的示例数量。k=1
)# 选择与输入最相似的示例。
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：

Running Chroma using direct local API.
Using DuckDB in-memory for database. Data will be transient.
Examples most similar to the input: Who was the father of Mary Ball Washington?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

我们还可以将示例选择器应用于FewShotPromptTemplate。创建一个FewShotPromptTemplate对象。该对象接收示例选择器和用于Few-Shot示例的格式化程序：

prompt = FewShotPromptTemplate(example_selector=example_selector, example_prompt=example_prompt, suffix="Question: {input}", input_variables=["input"]
)print(prompt.format(input="Who was the father of Mary Ball Washington?"))

输出：

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?

参考文献：
[1] LangChain 🦜️🔗 中文网，跟着LangChain一起学LLM/GPT开发：https://www.langchain.com.cn/
[2] LangChain中文网 - LangChain 是一个用于开发由语言模型驱动的应用程序的框架：http://www.cnlangchain.com/