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MarkdownHeaderTextSplitter

动机​

许多聊天或问答应用程序在嵌入和向量存储之前会对输入文档进行分块。

Pinecone的这些笔记提供了一些有用的提示：

当嵌入整个段落或文档时，嵌入过程会考虑文本中句子和短语之间的整体上下文和关系。这可能会导致更全面的向量表示，捕捉到文本的更广泛的含义和主题。

正如前面提到的，分块通常旨在将具有共同上下文的文本保持在一起。

考虑到这一点，我们可能希望特别尊重文档本身的结构。

例如，一个Markdown文件是按照标题组织的。

在特定的标题组中创建分块是一个直观的想法。

为了解决这个挑战，我们可以使用MarkdownHeaderTextSplitter。

这将根据指定的一组标题来拆分Markdown文件。

例如，如果我们想要拆分这个Markdown：

md = '# Foo\n\n ## Bar\n\nHi this is Jim  \nHi this is Joe\n\n ## Baz\n\n Hi this is Molly'

我们可以指定要拆分的标题：

[("#", "Header 1"),("##", "Header 2")]

然后，内容将根据共同的标题进行分组或拆分：

{'content': 'Hi this is Jim  \nHi this is Joe', 'metadata': {'Header 1': 'Foo', 'Header 2': 'Bar'}}
{'content': 'Hi this is Molly', 'metadata': {'Header 1': 'Foo', 'Header 2': 'Baz'}}

让我们来看一些下面的示例：

from langchain.text_splitter import MarkdownHeaderTextSplitter

API参考：​

markdown_document = "# Foo\n\n    ## Bar\n\nHi this is Jim\n\nHi this is Joe\n\n ### Boo \n\n Hi this is Lance \n\n ## Baz\n\n Hi this is Molly"

headers_to_split_on = [
    ("#", "Header 1"),
    ("##", "Header 2"),
    ("###", "Header 3"),
]

markdown_splitter = MarkdownHeaderTextSplitter(headers_to_split_on=headers_to_split_on)
md_header_splits = markdown_splitter.split_text(markdown_document)
md_header_splits
[Document(page_content='Hi this is Jim  \nHi this is Joe', metadata={'Header 1': 'Foo', 'Header 2': 'Bar'}),
 Document(page_content='Hi this is Lance', metadata={'Header 1': 'Foo', 'Header 2': 'Bar', 'Header 3': 'Boo'}),
 Document(page_content='Hi this is Molly', metadata={'Header 1': 'Foo', 'Header 2': 'Baz'})]
type(md_header_splits[0])
langchain.schema.Document

在每个Markdown组中，我们可以应用任何我们想要的文本分割器。

markdown_document = "# Intro \n\n    ## History \n\n Markdown[9] is a lightweight markup language for creating formatted text using a plain-text editor. John Gruber created Markdown in 2004 as a markup language that is appealing to human readers in its source code form.[9] \n\n Markdown is widely used in blogging, instant messaging, online forums, collaborative software, documentation pages, and readme files. \n\n ## Rise and divergence \n\n As Markdown popularity grew rapidly, many Markdown implementations appeared, driven mostly by the need for \n\n additional features such as tables, footnotes, definition lists,[note 1] and Markdown inside HTML blocks. \n\n #### Standardization \n\n From 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardisation effort. \n\n ## Implementations \n\n Implementations of Markdown are available for over a dozen programming languages."

headers_to_split_on = [
    ("#", "Header 1"),
    ("##", "Header 2"),
]

# MD拆分
markdown_splitter = MarkdownHeaderTextSplitter(headers_to_split_on=headers_to_split_on)
md_header_splits = markdown_splitter.split_text(markdown_document)

# 字符级拆分
from langchain.text_splitter import RecursiveCharacterTextSplitter

chunk_size = 250
chunk_overlap = 30
text_splitter = RecursiveCharacterTextSplitter(
    chunk_size=chunk_size, chunk_overlap=chunk_overlap
)

# 拆分
splits = text_splitter.split_documents(md_header_splits)
splits

API参考：​

[Document(page_content='Markdown[9] is a lightweight markup language for creating formatted text using a plain-text editor. John Gruber created Markdown in 2004 as a markup language that is appealing to human readers in its source code form.[9]', metadata={'Header 1': 'Intro', 'Header 2': 'History'}),
 Document(page_content='Markdown is widely used in blogging, instant messaging, online forums, collaborative software, documentation pages, and readme files.', metadata={'Header 1': 'Intro', 'Header 2': 'History'}),
 Document(page_content='As Markdown popularity grew rapidly, many Markdown implementations appeared, driven mostly by the need for  \nadditional features such as tables, footnotes, definition lists,[note 1] and Markdown inside HTML blocks.  \n#### Standardization', metadata={'Header 1': 'Intro', 'Header 2': 'Rise and divergence'}),
 Document(page_content='#### Standardization  \nFrom 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardisation effort.', metadata={'Header 1': 'Intro', 'Header 2': 'Rise and divergence'}),
 Document(page_content='Implementations of Markdown are available for over a dozen programming languages.', metadata={'Header 1': 'Intro', 'Header 2': 'Implementations'})]