langchain/docs/snippets/modules/chains/get_started.mdx

#### Using `LLMChain`

The `LLMChain` is most basic building block chain. It takes in a prompt template, formats it with the user input and returns the response from an LLM.

To use the `LLMChain`, first create a prompt template.

```python
from langchain.llms import OpenAI
from langchain.prompts import PromptTemplate

llm = OpenAI(temperature=0.9)
prompt = PromptTemplate(
    input_variables=["product"],
    template="What is a good name for a company that makes {product}?",
)
```

We can now create a very simple chain that will take user input, format the prompt with it, and then send it to the LLM.


```python
from langchain.chains import LLMChain
chain = LLMChain(llm=llm, prompt=prompt)

# Run the chain only specifying the input variable.
print(chain.run("colorful socks"))
```

<CodeOutputBlock lang="python">

```
    Colorful Toes Co.
```

</CodeOutputBlock>

If there are multiple variables, you can input them all at once using a dictionary.


```python
prompt = PromptTemplate(
    input_variables=["company", "product"],
    template="What is a good name for {company} that makes {product}?",
)
chain = LLMChain(llm=llm, prompt=prompt)
print(chain.run({
    'company': "ABC Startup",
    'product': "colorful socks"
    }))
```

<CodeOutputBlock lang="python">

```
    Socktopia Colourful Creations.
```

</CodeOutputBlock>

You can use a chat model in an `LLMChain` as well:


```python
from langchain.chat_models import ChatOpenAI
from langchain.prompts.chat import (
    ChatPromptTemplate,
    HumanMessagePromptTemplate,
)
human_message_prompt = HumanMessagePromptTemplate(
        prompt=PromptTemplate(
            template="What is a good name for a company that makes {product}?",
            input_variables=["product"],
        )
    )
chat_prompt_template = ChatPromptTemplate.from_messages([human_message_prompt])
chat = ChatOpenAI(temperature=0.9)
chain = LLMChain(llm=chat, prompt=chat_prompt_template)
print(chain.run("colorful socks"))
```

<CodeOutputBlock lang="python">

```
    Rainbow Socks Co.
```

</CodeOutputBlock>