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核心模块（Modules)
模型 I/O（ModelIO）
大语言模型（Llms）
快速开始（QuickStart）

快速开始

大语言模型（LLM）是 LangChain 的核心组件。 LangChain 不提供自己的 LLM，而是提供一个标准接口来与许多不同的 LLM 交互。

有许多 LLM 提供方（OpenAI、Cohere、Hugging Face 等）——LLM 类旨在为它们全部提供一个标准接口。

本次演练中我们将使用一个 OpenAI LLM 封装，不过所展示的功能对所有 LLM 类型都是通用的。

设置

本例中我们需要安装 OpenAI Python 包：

pip install openai

访问 API 需要一个 API 密钥，你可以通过创建账户并前往 此处 (opens in a new tab) 获取。拿到密钥后，我们想通过运行以下命令将其设置为环境变量：

export OPENAI_API_KEY="..."

如果你不想设置环境变量，可以在初始化 OpenAI LLM 类时通过名为 api_key 的参数直接传入密钥：

from langchain_openai import OpenAI
 
llm = OpenAI(api_key="...")

否则你可以不带任何参数初始化：

from langchain_openai import OpenAI
 
llm = OpenAI()

LCEL

LLM 实现了 Runnable 接口，它是 LangChain 表达式语言（LCEL） 的基本构建块。这意味着它们支持 invoke、ainvoke、stream、astream、batch、abatch、astream_log 调用。

LLM 接受 字符串 作为输入，或接受可被强制转换为字符串提示的对象，包括 List[BaseMessage] 和 PromptValue。

llm.invoke(
    "What are some theories about the relationship between unemployment and inflation?"
)
'\n\n1. The Phillips Curve Theory: This suggests that there is an inverse relationship between unemployment and inflation, meaning that when unemployment is low, inflation will be higher, and when unemployment is high, inflation will be lower.\n\n2. The Monetarist Theory: This theory suggests that the relationship between unemployment and inflation is weak, and that changes in the money supply are more important in determining inflation.\n\n3. The Resource Utilization Theory: This suggests that when unemployment is low, firms are able to raise wages and prices in order to take advantage of the increased demand for their products and services. This leads to higher inflation.'
for chunk in llm.stream(
    "What are some theories about the relationship between unemployment and inflation?"
):
    print(chunk, end="", flush=True)

1. The Phillips Curve Theory: This theory states that there is an inverse relationship between unemployment and inflation. As unemployment decreases, inflation increases and vice versa.

2. The Cost-Push Inflation Theory: This theory suggests that an increase in unemployment leads to a decrease in aggregate demand, which causes prices to go up due to a decrease in supply.

3. The Wage-Push Inflation Theory: This theory states that when unemployment is low, wages tend to increase due to competition for labor, which causes prices to rise.

4. The Monetarist Theory: This theory states that there is no direct relationship between unemployment and inflation, but rather, an increase in the money supply leads to inflation, which can be caused by an increase in unemployment.

llm.batch(
    [
        "What are some theories about the relationship between unemployment and inflation?"
    ]
)
['\n\n1. The Phillips Curve Theory: This theory suggests that there is an inverse relationship between unemployment and inflation, meaning that when unemployment decreases, inflation rises, and when unemployment increases, inflation decreases. This theory is based on the idea that when the economy is doing well, there is more demand for goods and services, causing prices to increase.\n\n2. The Cost-Push Theory: This theory suggests that when the cost of production increases, it leads to higher prices and lower output. This can lead to higher unemployment and eventually higher inflation.\n\n3. The Demand-Pull Theory: This theory suggests that when demand for goods and services increases, it leads to higher prices and eventually higher inflation. This can lead to higher unemployment as businesses cannot keep up with the higher demand.\n\n4. The Structural Unemployment Theory: This theory suggests that when there is a mismatch between the skills of the unemployed and the skills required in the job market, it leads to higher unemployment and eventually higher inflation.']
await llm.ainvoke(
    "What are some theories about the relationship between unemployment and inflation?"
)
'\n\n1. Phillips Curve Theory: This theory states that there is an inverse relationship between inflation and unemployment. As unemployment decreases, inflation increases, and vice versa.\n\n2. Cost-Push Theory: This theory suggests that inflation is caused by rising costs, which can be caused by an increase in unemployment. As unemployment rises, businesses are unable to keep up with demand and have to raise prices to compensate.\n\n3. Demand-Pull Theory: This theory suggests that inflation occurs when demand exceeds supply. As unemployment increases, demand for goods and services decreases, leading to a decrease in inflation.\n\n4. Monetary Theory: This theory suggests that the money supply and inflation are related to unemployment. When the money supply increases, prices increase, leading to an increase in inflation. If unemployment is high, then the money supply increases, leading to an increase in inflation.'
async for chunk in llm.astream(
    "What are some theories about the relationship between unemployment and inflation?"
):
    print(chunk, end="", flush=True)

1. Phillips Curve Theory: This theory suggests that there is an inverse relationship between unemployment and inflation, meaning that when unemployment is low, inflation rises and vice versa.

2. Cost-Push Theory: This theory suggests that inflation is caused by rising costs of production, such as wages, raw materials, and energy. It states that when costs increase, firms must pass these costs onto the consumer, thus raising the price of goods and services and leading to inflation.

3. Demand-Pull Theory: This theory suggests that inflation is caused by an increase in demand for goods and services, leading to a rise in prices. It suggests that when unemployment is low, people have more money to spend and this increased demand pushes up prices.

4. Monetarist Theory: This theory states that inflation is caused by an increase in the money supply. It suggests that when the money supply increases, people have more money to spend, leading to higher prices.

await llm.abatch(
    [
        "What are some theories about the relationship between unemployment and inflation?"
    ]
)
['\n\n1. The Phillips Curve Theory: This theory states that there is an inverse relationship between unemployment and inflation. When unemployment is low, wages increase, leading to higher prices and overall inflation.\n\n2. The Cost-Push Theory: This theory states that inflation is caused by increases in the costs of production, such as wages, goods, and services. When the cost of production increases, the prices of goods and services must also increase, leading to inflation.\n\n3. The Demand Pull Theory: This theory states that inflation is caused by an increase in aggregate demand for goods and services. When the demand is high, prices must increase in order to meet the demand. This leads to inflation.\n\n4. The Structural Unemployment Theory: This theory states that when unemployment is high, there is an excess supply of labor. This excess supply of labor can result in lower wages, which can cause inflation as people are willing to accept lower wages for the same amount of work.']
async for chunk in llm.astream_log(
    "What are some theories about the relationship between unemployment and inflation?"
):
    print(chunk)
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' unemployment'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ','})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' also'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' known'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' the'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' Non'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': '-'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': 'Ac'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': 'celer'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' In'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': 'flation'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' Rate'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' of'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' Unemployment'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' theory'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' when'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' unemployment'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' is'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' then'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' inflation'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ','})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' when'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' unemployment'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ','})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' inflation'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ','})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' which'})
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RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' prices'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ' and higher inflation'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': '.'})
RunLogPatch({'op': 'add', 'path': '/streamed_output/-', 'value': ''})
RunLogPatch({'op': 'replace',
  'path': '/final_output',
  'value': {'generations': [[{'generation_info': {'finish_reason': 'stop',
                                                  'logprobs': None},
                              'text': '\n'
                                      '\n'
                                      '1. The Phillips Curve: This theory '
                                      'suggests that there is an inverse '
                                      'relationship between unemployment and '
                                      'inflation. When unemployment is low, '
                                      'inflation tends to be high, and when '
                                      'unemployment is high, inflation tends '
                                      'to be low. \n'
                                      '\n'
                                      '2. The NAIRU Theory: This theory '
                                      'suggests that there is a natural rate '
                                      'of unemployment, also known as the '
                                      'Non-Accelerating Inflation Rate of '
                                      'Unemployment (NAIRU). According to this '
                                      'theory, when unemployment is below the '
                                      'NAIRU, then inflation will increase, '
                                      'and when unemployment is above the '
                                      'NAIRU, then inflation will decrease.\n'
                                      '\n'
                                      '3. The Cost-Push Inflation Theory: This '
                                      'theory suggests that high unemployment '
                                      'leads to higher wages, which in turn '
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LangSmith

所有 LLM 都内置了 LangSmith 追踪。只需设置以下环境变量：

export LANGCHAIN_TRACING_V2="true"
export LANGCHAIN_API_KEY=<your-api-key>

任何 LLM 调用（无论是否嵌套在链中）都会被自动追踪。一次追踪将包含输入、输出、延迟、令牌用量、调用参数、环境参数等。参见这里的示例：https://smith.langchain.com/public/7924621a-ff58-4b1c-a2a2-035a354ef434/r。 (opens in a new tab)

之后你可以在 LangSmith 中为任何追踪提供反馈、为评估编译带标注的数据集、在 playground 中调试性能等等。

索引（Index）自定义大语言模型（CustomLlm）