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Langchain

LangchainOutputParser #

Bases: ChainableOutputParser

Langchain output parser.

Source code in llama-index-integrations/output_parsers/llama-index-output-parsers-langchain/llama_index/output_parsers/langchain/base.py 
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class LangchainOutputParser(ChainableOutputParser):
    """Langchain output parser."""

    def __init__(
        self, output_parser: "LCOutputParser", format_key: Optional[str] = None
    ) -> None:
        """Init params."""
        self._output_parser = output_parser
        self._format_key = format_key

    def parse(self, output: str) -> Any:
        """Parse, validate, and correct errors programmatically."""
        # TODO: this object may be stringified by our upstream llmpredictor,
        # figure out better
        # ways to "convert" the object to a proper string format.
        return self._output_parser.parse(output)

    def format(self, query: str) -> str:
        """Format a query with structured output formatting instructions."""
        format_instructions = self._output_parser.get_format_instructions()

        # TODO: this is a temporary hack. if there's curly brackets in the format
        # instructions (and query is a string template), we need to
        # escape the curly brackets in the format instructions to preserve the
        # overall template.
        query_tmpl_vars = {
            v for _, v, _, _ in Formatter().parse(query) if v is not None
        }
        if len(query_tmpl_vars) > 0:
            format_instructions = format_instructions.replace("{", "{{")
            format_instructions = format_instructions.replace("}", "}}")

        if self._format_key is not None:
            fmt_query = query.format(**{self._format_key: format_instructions})
        else:
            fmt_query = query + "\n\n" + format_instructions

        return fmt_query

parse #

parse(output: str) -> Any

Parse, validate, and correct errors programmatically.

Source code in llama-index-integrations/output_parsers/llama-index-output-parsers-langchain/llama_index/output_parsers/langchain/base.py 
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def parse(self, output: str) -> Any:
    """Parse, validate, and correct errors programmatically."""
    # TODO: this object may be stringified by our upstream llmpredictor,
    # figure out better
    # ways to "convert" the object to a proper string format.
    return self._output_parser.parse(output)

format #

format(query: str) -> str

Format a query with structured output formatting instructions.

Source code in llama-index-integrations/output_parsers/llama-index-output-parsers-langchain/llama_index/output_parsers/langchain/base.py 
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def format(self, query: str) -> str:
    """Format a query with structured output formatting instructions."""
    format_instructions = self._output_parser.get_format_instructions()

    # TODO: this is a temporary hack. if there's curly brackets in the format
    # instructions (and query is a string template), we need to
    # escape the curly brackets in the format instructions to preserve the
    # overall template.
    query_tmpl_vars = {
        v for _, v, _, _ in Formatter().parse(query) if v is not None
    }
    if len(query_tmpl_vars) > 0:
        format_instructions = format_instructions.replace("{", "{{")
        format_instructions = format_instructions.replace("}", "}}")

    if self._format_key is not None:
        fmt_query = query.format(**{self._format_key: format_instructions})
    else:
        fmt_query = query + "\n\n" + format_instructions

    return fmt_query