# PAL（程序辅助语言模型）

import { Callout, FileTree } from 'nextra-theme-docs'
import {Screenshot} from 'components/screenshot'
import PAL from '../../img/pal.png'

[Gao 等人（2022）](https://arxiv.org/abs/2211.10435)提出了一种使用 LLMs 读取自然语言问题并生成程序作为中间推理步骤的方法。被称为程序辅助语言模型（PAL），它与思维链提示不同，因为它不是使用自由形式文本来获得解决方案，而是将解决步骤卸载到类似 Python 解释器的编程运行时中。

<Screenshot src={PAL} alt="PAL" />
图片来源：[Gao 等人（2022）](https://arxiv.org/abs/2211.10435)

让我们以 LangChain 和 OpenAI GPT-3 为例。我们有兴趣开发一个简单的应用程序，它能够解释所提出的问题，并利用 Python 解释器提供答案。

具体来说，我们有兴趣创建一个功能，允许使用 LLM 回答需要日期理解的问题。我们将为 LLM 提供一个提示，其中包括一些示例，这些示例是从[这里](https://github.com/reasoning-machines/pal/blob/main/pal/prompt/date_understanding_prompt.py)采用的。

这是我们需要导入的包：

```python
import openai
from datetime import datetime
from dateutil.relativedelta import relativedelta
import os
from langchain.llms import OpenAI
from dotenv import load_dotenv
```

让我们先配置一些环境：

```python
load_dotenv()

# API configuration
openai.api_key = os.getenv("OPENAI_API_KEY")

# for LangChain
os.environ["OPENAI_API_KEY"] = os.getenv("OPENAI_API_KEY")
```

设置模型实例：

```python
llm = OpenAI(model_name='text-davinci-003', temperature=0)
```

设置提示+问题：

```python
question = "Today is 27 February 2023. I was born exactly 25 years ago. What is the date I was born in MM/DD/YYYY?"

DATE_UNDERSTANDING_PROMPT = """
# Q: 2015 is coming in 36 hours. What is the date one week from today in MM/DD/YYYY?
# If 2015 is coming in 36 hours, then today is 36 hours before.
today = datetime(2015, 1, 1) - relativedelta(hours=36)
# One week from today,
one_week_from_today = today + relativedelta(weeks=1)
# The answer formatted with %m/%d/%Y is
one_week_from_today.strftime('%m/%d/%Y')
# Q: The first day of 2019 is a Tuesday, and today is the first Monday of 2019. What is the date today in MM/DD/YYYY?
# If the first day of 2019 is a Tuesday, and today is the first Monday of 2019, then today is 6 days later.
today = datetime(2019, 1, 1) + relativedelta(days=6)
# The answer formatted with %m/%d/%Y is
today.strftime('%m/%d/%Y')
# Q: The concert was scheduled to be on 06/01/1943, but was delayed by one day to today. What is the date 10 days ago in MM/DD/YYYY?
# If the concert was scheduled to be on 06/01/1943, but was delayed by one day to today, then today is one day later.
today = datetime(1943, 6, 1) + relativedelta(days=1)
# 10 days ago,
ten_days_ago = today - relativedelta(days=10)
# The answer formatted with %m/%d/%Y is
ten_days_ago.strftime('%m/%d/%Y')
# Q: It is 4/19/1969 today. What is the date 24 hours later in MM/DD/YYYY?
# It is 4/19/1969 today.
today = datetime(1969, 4, 19)
# 24 hours later,
later = today + relativedelta(hours=24)
# The answer formatted with %m/%d/%Y is
today.strftime('%m/%d/%Y')
# Q: Jane thought today is 3/11/2002, but today is in fact Mar 12, which is 1 day later. What is the date 24 hours later in MM/DD/YYYY?
# If Jane thought today is 3/11/2002, but today is in fact Mar 12, then today is 3/12/2002.
today = datetime(2002, 3, 12)
# 24 hours later,
later = today + relativedelta(hours=24)
# The answer formatted with %m/%d/%Y is
later.strftime('%m/%d/%Y')
# Q: Jane was born on the last day of Feburary in 2001. Today is her 16-year-old birthday. What is the date yesterday in MM/DD/YYYY?
# If Jane was born on the last day of Feburary in 2001 and today is her 16-year-old birthday, then today is 16 years later.
today = datetime(2001, 2, 28) + relativedelta(years=16)
# Yesterday,
yesterday = today - relativedelta(days=1)
# The answer formatted with %m/%d/%Y is
yesterday.strftime('%m/%d/%Y')
# Q: {question}
""".strip() + '\n'
```

```python
llm_out = llm(DATE_UNDERSTANDING_PROMPT.format(question=question))
print(llm_out)
```

这将输出以下内容：
```
# If today is 27 February 2023 and I was born exactly 25 years ago, then I was born 25 years before.
today = datetime(2023, 2, 27)
# I was born 25 years before,
born = today - relativedelta(years=25)
# The answer formatted with %m/%d/%Y is
born.strftime('%m/%d/%Y')
```

`llm_out` 是一段 `python` 代码，我们可以使用 `exec` 执行它：

```python
exec(llm_out)
print(born)
```

这将输出以下内容：`02/27/1998`
