Harrison/load from hub (#580)

langchain/prompts/__init__.py

@@ -1,7 +1,7 @@
 """Prompt template classes."""
 from langchain.prompts.base import BasePromptTemplate
 from langchain.prompts.few_shot import FewShotPromptTemplate
-from langchain.prompts.loading import load_prompt
+from langchain.prompts.loading import load_from_hub, load_prompt
 from langchain.prompts.prompt import Prompt, PromptTemplate
 
 __all__ = [
@@ -10,4 +10,5 @@ __all__ = [
     "PromptTemplate",
     "FewShotPromptTemplate",
     "Prompt",
+    "load_from_hub",
 ]

langchain/prompts/loading.py

@@ -1,8 +1,11 @@
 """Load prompts from disk."""
+import importlib
 import json
+import tempfile
 from pathlib import Path
 from typing import Union
 
+import requests
 import yaml
 
 from langchain.prompts.base import BasePromptTemplate
@@ -97,7 +100,38 @@ def load_prompt(file: Union[str, Path]) -> BasePromptTemplate:
     elif file_path.suffix == ".yaml":
         with open(file_path, "r") as f:
             config = yaml.safe_load(f)
+    elif file_path.suffix == ".py":
+        spec = importlib.util.spec_from_loader(
+            "prompt", loader=None, origin=str(file_path)
+        )
+        if spec is None:
+            raise ValueError("could not load spec")
+        helper = importlib.util.module_from_spec(spec)
+        with open(file_path, "rb") as f:
+            exec(f.read(), helper.__dict__)
+        if not isinstance(helper.PROMPT, BasePromptTemplate):
+            raise ValueError("Did not get object of type BasePromptTemplate.")
+        return helper.PROMPT
     else:
-        raise ValueError
+        raise ValueError(f"Got unsupported file type {file_path.suffix}")
     # Load the prompt from the config now.
     return load_prompt_from_config(config)
+
+
+URL_BASE = "https://raw.githubusercontent.com/hwchase17/langchain-hub/master/prompts/"
+
+
+def load_from_hub(path: str) -> BasePromptTemplate:
+    """Load prompt from hub."""
+    suffix = path.split(".")[-1]
+    if suffix not in {"py", "json", "yaml"}:
+        raise ValueError("Unsupported file type.")
+    full_url = URL_BASE + path
+    r = requests.get(full_url)
+    if r.status_code != 200:
+        raise ValueError(f"Could not find file at {full_url}")
+    with tempfile.TemporaryDirectory() as tmpdirname:
+        file = tmpdirname + "/prompt." + suffix
+        with open(file, "wb") as f:
+            f.write(r.content)
+        return load_prompt(file)