Class PromptTemplate

libs/core/langchain_core/prompts/prompt.py:19–275

Prompt template for a language model. A prompt template consists of a string template. It accepts a set of parameters from the user that can be used to generate a prompt for a language model. The template can be formatted using either f-strings (default) or jinja2 syntax. *Securit

class PromptTemplate(StringPromptTemplate):
    """Prompt template for a language model.

    A prompt template consists of a string template. It accepts a set of parameters
    from the user that can be used to generate a prompt for a language model.

    The template can be formatted using either f-strings (default) or jinja2 syntax.

    *Security warning*: Prefer using `template_format="f-string"` instead of
        `template_format="jinja2"`, or make sure to NEVER accept jinja2 templates
        from untrusted sources as they may lead to arbitrary Python code execution.

        As of LangChain 0.0.329, Jinja2 templates will be rendered using
        Jinja2's SandboxedEnvironment by default. This sand-boxing should
        be treated as a best-effort approach rather than a guarantee of security,
        as it is an opt-out rather than opt-in approach.

        Despite the sand-boxing, we recommend to never use jinja2 templates
        from untrusted sources.

    Example:

        .. code-block:: python

            from langchain_core.prompts import PromptTemplate

            # Instantiation using from_template (recommended)
            prompt = PromptTemplate.from_template("Say {foo}")
            prompt.format(foo="bar")

            # Instantiation using initializer
            prompt = PromptTemplate(template="Say {foo}")
    """

    @property
    def lc_attributes(self) -> Dict[str, Any]:
        return {
            "template_format": self.template_format,
        }

    @classmethod
    def get_lc_namespace(cls) -> List[str]:
        """Get the namespace of the langchain object."""
        return ["langchain", "prompts", "prompt"]

    input_variables: List[str]
    """A list of the names of the variables the prompt template expects."""

    template: str
    """The prompt template."""

    template_format: Literal["f-string", "mustache", "jinja2"] = "f-string"
    """The format of the prompt template.
    Options are: 'f-string', 'mustache', 'jinja2'."""

    validate_template: bool = False
    """Whether or not to try validating the template."""