vformat() — langchain Function Reference

Architecture documentation for the vformat() function in formatting.py from the langchain codebase.

Function python Observability TelemetryUtilities

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Observability→ TelemetryUtilities→ vformat() — langchain Function Reference

Dependency Diagram

graph TD
  8fbd4e04_2653_02f4_eac0_0f96887f3f7f["vformat()"]
  29112ca2_d607_429e_5319_09bd1ea18686["StrictFormatter"]
  8fbd4e04_2653_02f4_eac0_0f96887f3f7f -->|defined in| 29112ca2_d607_429e_5319_09bd1ea18686
  style 8fbd4e04_2653_02f4_eac0_0f96887f3f7f fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/core/langchain_core/utils/formatting.py lines 23–48

    def vformat(
        self, format_string: str, args: Sequence, kwargs: Mapping[str, Any]
    ) -> str:
        """Format a string using only keyword arguments.

        Overrides the base `vformat` to reject positional arguments, ensuring all
        substitutions are explicit and named.

        Args:
            format_string: A string containing replacement fields (e.g., `'{name}'`).
            args: Positional arguments (must be empty).
            kwargs: Keyword arguments for substitution into the format string.

        Returns:
            The formatted string with all replacement fields substituted.

        Raises:
            ValueError: If any positional arguments are provided.
        """
        if len(args) > 0:
            msg = (
                "No arguments should be provided, "
                "everything should be passed as keyword arguments."
            )
            raise ValueError(msg)
        return super().vformat(format_string, args, kwargs)