DynamicPrompt class creation

langchain/__init__.py

@@ -17,7 +17,7 @@
 from langchain.docstore import Wikipedia
 from langchain.faiss import FAISS
 from langchain.llms import Cohere, HuggingFaceHub, OpenAI
-from langchain.prompt import Prompt
+from langchain.prompt import DynamicPrompt, Prompt
 from langchain.sql_database import SQLDatabase
 
 __all__ = [
@@ -28,6 +28,7 @@
     "SerpAPIChain",
     "Cohere",
     "OpenAI",
+    "DynamicPrompt",
     "Prompt",
     "ReActChain",
     "Wikipedia",

langchain/prompt.py

@@ -101,3 +101,102 @@ def from_examples(
         example_str = example_separator.join(examples)
         template = prefix + example_str + suffix
         return cls(input_variables=input_variables, template=template)
+
+
+class DynamicPrompt(BaseModel):
+    r"""Schema to represent a dynamic prompt for an LLM.
+
+    Example:
+        .. code-block:: python
+
+            from langchain import DynamicPrompt
+            dynamic_prompt = DynamicPrompt(
+                examples=["Say hi. Hi", "Say ho. Ho"],
+                example_separator="\n\n",
+                prefix="",
+                suffix="\n\nSay {foo}"
+                input_variables=["foo"]
+            )
+    """
+
+    examples: List[str]
+    """A list of the examples that the prompt template expects."""
+
+    example_separator: str
+    """Example separator, e.g. \n\n, for the dynamic prompt creation."""
+
+    input_variables: List[str]
+    """A list of the names of the variables the prompt template expects."""
+
+    prefix: str
+    """Prefix for the prompt."""
+
+    suffix: str
+    """Suffix for the prompt."""
+
+    template_format: str = "f-string"
+    """The format of the prompt template. Options are: 'f-string'."""
+
+    class Config:
+        """Configuration for this pydantic object."""
+
+        extra = Extra.forbid
+
+    def format(self, **kwargs: Any) -> str:
+        """Dynamically format the prompt with the inputs.
+
+        Args:
+            kwargs: Any arguments to be passed to the prompt template.
+
+        Returns:
+            A formatted string.
+
+        Example:
+
+        .. code-block:: python
+
+            prompt.format(variable1="foo")
+        """
+        # TODO segment self.examples based on example length &
+        # input_variables length here
+        example_str = self.example_separator.join(self.examples)
+        template = self.prefix + example_str + self.suffix
+        return _FORMATTER_MAPPING[self.template_format](template, **kwargs)
+
+    @root_validator()
+    def template_is_valid(cls, values: Dict) -> Dict:
+        """Check that suffix and input variables are consistent."""
+        input_variables = values["input_variables"]
+        suffix = values["suffix"]
+        template_format = values["template_format"]
+        if template_format not in _FORMATTER_MAPPING:
+            valid_formats = list(_FORMATTER_MAPPING)
+            raise ValueError(
+                f"Invalid template format. Got `{template_format}`;"
+                f" should be one of {valid_formats}"
+            )
+        dummy_inputs = {input_variable: "foo" for input_variable in input_variables}
+        try:
+            formatter_func = _FORMATTER_MAPPING[template_format]
+            formatter_func(suffix, **dummy_inputs)
+        except KeyError:
+            raise ValueError("Invalid prompt schema.")
+        return values
+
+    @classmethod
+    def from_examples(
+        cls,
+        examples: List[str],
+        suffix: str,
+        input_variables: List[str],
+        example_separator: str = "\n\n",
+        prefix: str = "",
+    ) -> "DynamicPrompt":
+        """Initialize DynamicPrompt with prefix, suffix, examples, etc."""
+        return cls(
+            examples=examples,
+            example_separator=example_separator,
+            input_variables=input_variables,
+            prefix=prefix,
+            suffix=suffix,
+        )