From 7658263bfbc9485ebbc85b7d4c2476ea68611e26 Mon Sep 17 00:00:00 2001
From: Bagatur <22008038+baskaryan@users.noreply.github.com>
Date: Sat, 4 Feb 2023 22:49:17 -0800
Subject: [PATCH] Check type of LLM.generate `prompts` arg (#886)

Was passing prompt in directly as string and getting nonsense outputs.
Had to inspect source code to realize that first arg should be a list.
Could be nice if there was an explicit error or warning, seems like this
could be a common mistake.
---
 langchain/llms/base.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/langchain/llms/base.py b/langchain/llms/base.py
index 06c57153..269cdd77 100644
--- a/langchain/llms/base.py
+++ b/langchain/llms/base.py
@@ -62,6 +62,13 @@ class BaseLLM(BaseModel, ABC):
         self, prompts: List[str], stop: Optional[List[str]] = None
     ) -> LLMResult:
         """Run the LLM on the given prompt and input."""
+        # If string is passed in directly no errors will be raised but outputs will
+        # not make sense.
+        if not isinstance(prompts, list):
+            raise ValueError(
+                "Argument 'prompts' is expected to be of type List[str], received"
+                f" argument of type {type(prompts)}."
+            )
         disregard_cache = self.cache is not None and not self.cache
         if langchain.llm_cache is None or disregard_cache:
             # This happens when langchain.cache is None, but self.cache is True