format_document#

langchain_core.prompts.base.format_document(doc: Document, prompt: BasePromptTemplate[str]) → str[source]#

Format a document into a string based on a prompt template.

First, this pulls information from the document from two sources:

  1. page_content:

    This takes the information from the document.page_content and assigns it to a variable named page_content.

  2. metadata:

    This takes information from document.metadata and assigns it to variables of the same name.

Those variables are then passed into the prompt to produce a formatted string.

Parameters:

  • doc (Document) – Document, the page_content and metadata will be used to create the final string.

  • prompt (BasePromptTemplate[str]) – BasePromptTemplate, will be used to format the page_content and metadata into the final string.

Returns:

string of the document formatted.

Return type:

str

Example

from langchain_core.documents import Document
from langchain_core.prompts import PromptTemplate

doc = Document(page_content="This is a joke", metadata={"page": "1"})
prompt = PromptTemplate.from_template("Page {page}: {page_content}")
format_document(doc, prompt)
>>> "Page 1: This is a joke"
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