load agents from hub (#759)

langchain/agents/loading.py

@@ -1,8 +1,11 @@
 """Functionality for loading agents."""
 import json
+import os
+import tempfile
 from pathlib import Path
 from typing import Any, Union
 
+import requests
 import yaml
 
 from langchain.agents.agent import Agent
@@ -19,6 +22,8 @@ AGENT_TO_CLASS = {
     "conversational-react-description": ConversationalAgent,
 }
 
+URL_BASE = "https://raw.githubusercontent.com/hwchase17/langchain-hub/master/agents/"
+
 
 def load_agent_from_config(config: dict, **kwargs: Any) -> Agent:
     """Load agent from Config Dict."""
@@ -40,7 +45,32 @@ def load_agent_from_config(config: dict, **kwargs: Any) -> Agent:
     return agent_cls(**combined_config)  # type: ignore
 
 
-def load_agent(file: Union[str, Path], **kwargs: Any) -> Agent:
+def load_agent(path: Union[str, Path], **kwargs: Any) -> Agent:
+    """Unified method for loading a agent from LangChainHub or local fs."""
+    if isinstance(path, str) and path.startswith("lc://agents"):
+        path = os.path.relpath(path, "lc://agents/")
+        return _load_from_hub(path, **kwargs)
+    else:
+        return _load_agent_from_file(path, **kwargs)
+
+
+def _load_from_hub(path: str, **kwargs: Any) -> Agent:
+    """Load agent from hub."""
+    suffix = path.split(".")[-1]
+    if suffix not in {"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 + "/agent." + suffix
+        with open(file, "wb") as f:
+            f.write(r.content)
+        return _load_agent_from_file(file)
+
+
+def _load_agent_from_file(file: Union[str, Path], **kwargs: Any) -> Agent:
     """Load agent from file."""
     # Convert file to Path object.
     if isinstance(file, str):