format_messages() — langchain Function Reference

Architecture documentation for the format_messages() function in chat.py from the langchain codebase.

Function python PromptManagement ChatTemplates calls 1

Entity Profile

PromptManagement→ ChatTemplates→ format_messages() — langchain Function Reference

Dependency Diagram

graph TD
  262c7d87_05aa_3d71_5515_77e949d77865["format_messages()"]
  c5f45b6e_9126_7fa3_ba5a_e6a86d45b6d5["MessagesPlaceholder"]
  262c7d87_05aa_3d71_5515_77e949d77865 -->|defined in| c5f45b6e_9126_7fa3_ba5a_e6a86d45b6d5
  9e40405f_9251_5a40_24a2_2959e7b39db7["format_messages()"]
  262c7d87_05aa_3d71_5515_77e949d77865 -->|calls| 9e40405f_9251_5a40_24a2_2959e7b39db7
  style 262c7d87_05aa_3d71_5515_77e949d77865 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/core/langchain_core/prompts/chat.py lines 163–189

    def format_messages(self, **kwargs: Any) -> list[BaseMessage]:
        """Format messages from kwargs.

        Args:
            **kwargs: Keyword arguments to use for formatting.

        Returns:
            List of `BaseMessage` objects.

        Raises:
            ValueError: If variable is not a list of messages.
        """
        value = (
            kwargs.get(self.variable_name, [])
            if self.optional
            else kwargs[self.variable_name]
        )
        if not isinstance(value, list):
            msg = (
                f"variable {self.variable_name} should be a list of base messages, "
                f"got {value} of type {type(value)}"
            )
            raise ValueError(msg)  # noqa: TRY004
        value = convert_to_messages(value)
        if self.n_messages:
            value = value[-self.n_messages :]
        return value