mirror of https://github.com/hwchase17/langchain
Add MimeType based parser (#4376)
# Add MimeType Based Parser This PR adds a MimeType Based Parser. The parser inspects the mime-type of the blob it is parsing and based on the mime-type can delegate to the sub parser. ## Before submitting Waiting on adding notebooks until more implementations are landed. ## Who can review? Community members can review the PR once tests pass. Tag maintainers/contributors who might be interested: @hwchase17 @vowelparrotpull/4408/head
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"""Code for generic / auxiliary parsers.
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This module contains some logic to help assemble more sophisticated parsers.
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"""
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from typing import Iterator, Mapping, Optional
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from langchain.document_loaders.base import BaseBlobParser
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from langchain.document_loaders.blob_loaders.schema import Blob
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from langchain.schema import Document
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class MimeTypeBasedParser(BaseBlobParser):
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"""A parser that uses mime-types to determine how to parse a blob.
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This parser is useful for simple pipelines where the mime-type is sufficient
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to determine how to parse a blob.
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To use, configure handlers based on mime-types and pass them to the initializer.
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Example:
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.. code-block:: python
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from langchain.document_loaders.parsers.generic import MimeTypeBasedParser
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parser = MimeTypeBasedParser(
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handlers={
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"application/pdf": ...,
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},
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fallback_parser=...,
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)
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"""
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def __init__(
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self,
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handlers: Mapping[str, BaseBlobParser],
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fallback_parser: Optional[BaseBlobParser] = None,
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) -> None:
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"""Define a parser that uses mime-types to determine how to parse a blob.
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Args:
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handlers: A mapping from mime-types to functions that take a blob, parse it
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and return a document.
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fallback_parser: A fallback_parser parser to use if the mime-type is not
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found in the handlers. If provided, this parser will be
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used to parse blobs with all mime-types not found in
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the handlers.
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If not provided, a ValueError will be raised if the
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mime-type is not found in the handlers.
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"""
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self.handlers = handlers
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self.fallback_parser = fallback_parser
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def lazy_parse(self, blob: Blob) -> Iterator[Document]:
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"""Load documents from a blob."""
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mimetype = blob.mimetype
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if mimetype is None:
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raise ValueError(f"{blob} does not have a mimetype.")
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if mimetype in self.handlers:
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handler = self.handlers[mimetype]
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yield from handler.lazy_parse(blob)
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else:
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if self.fallback_parser is not None:
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yield from self.fallback_parser.lazy_parse(blob)
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else:
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raise ValueError(f"Unsupported mime type: {mimetype}")
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"""Module to test generic parsers."""
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from typing import Iterator
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import pytest
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from langchain.document_loaders.base import BaseBlobParser
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from langchain.document_loaders.blob_loaders import Blob
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from langchain.document_loaders.parsers.generic import MimeTypeBasedParser
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from langchain.schema import Document
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class TestMimeBasedParser:
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"""Test mime based parser."""
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def test_without_fallback_parser(self) -> None:
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class FirstCharParser(BaseBlobParser):
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def lazy_parse(self, blob: Blob) -> Iterator[Document]:
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"""Extract the first character of a blob."""
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yield Document(page_content=blob.as_string()[0])
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class SecondCharParser(BaseBlobParser):
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def lazy_parse(self, blob: Blob) -> Iterator[Document]:
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"""Extract the second character of a blob."""
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yield Document(page_content=blob.as_string()[1])
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parser = MimeTypeBasedParser(
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handlers={
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"text/plain": FirstCharParser(),
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"text/html": SecondCharParser(),
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},
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)
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blob = Blob(data=b"Hello World", mimetype="text/plain")
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docs = parser.parse(blob)
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assert len(docs) == 1
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doc = docs[0]
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assert doc.page_content == "H"
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# Check text/html handler.
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blob = Blob(data=b"Hello World", mimetype="text/html")
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docs = parser.parse(blob)
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assert len(docs) == 1
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doc = docs[0]
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assert doc.page_content == "e"
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blob = Blob(data=b"Hello World", mimetype="text/csv")
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with pytest.raises(ValueError, match="Unsupported mime type"):
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# Check that the fallback parser is used when the mimetype is not found.
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parser.parse(blob)
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def test_with_fallback_parser(self) -> None:
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class FirstCharParser(BaseBlobParser):
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def lazy_parse(self, blob: Blob) -> Iterator[Document]:
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"""Extract the first character of a blob."""
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yield Document(page_content=blob.as_string()[0])
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class SecondCharParser(BaseBlobParser):
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def lazy_parse(self, blob: Blob) -> Iterator[Document]:
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"""Extract the second character of a blob."""
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yield Document(page_content=blob.as_string()[1])
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class ThirdCharParser(BaseBlobParser):
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def lazy_parse(self, blob: Blob) -> Iterator[Document]:
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"""Extract the third character of a blob."""
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yield Document(page_content=blob.as_string()[2])
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parser = MimeTypeBasedParser(
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handlers={
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"text/plain": FirstCharParser(),
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"text/html": SecondCharParser(),
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},
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fallback_parser=ThirdCharParser(),
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)
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blob = Blob(data=b"Hello World", mimetype="text/plain")
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docs = parser.parse(blob)
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assert len(docs) == 1
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doc = docs[0]
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assert doc.page_content == "H"
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# Check text/html handler.
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blob = Blob(data=b"Hello World", mimetype="text/html")
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docs = parser.parse(blob)
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assert len(docs) == 1
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doc = docs[0]
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assert doc.page_content == "e"
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# Check that the fallback parser is used when the mimetype is not found.
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blob = Blob(data=b"Hello World", mimetype="text/csv")
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docs = parser.parse(blob)
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assert len(docs) == 1
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doc = docs[0]
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assert doc.page_content == "l"
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