simplify parsing of the final answer (#621)

langchain/agents/mrkl/base.py

@@ -10,7 +10,7 @@
 from langchain.llms.base import BaseLLM
 from langchain.prompts import PromptTemplate
 
-FINAL_ANSWER_ACTION = "Final Answer: "
+FINAL_ANSWER_ACTION = "Final Answer:"
 
 
 class ChainConfig(NamedTuple):
@@ -30,7 +30,7 @@ class ChainConfig(NamedTuple):
 def get_action_and_input(llm_output: str) -> Tuple[str, str]:
     """Parse out the action and input from the LLM output."""
     if FINAL_ANSWER_ACTION in llm_output:
-        return "Final Answer", llm_output.split(FINAL_ANSWER_ACTION)[-1]
+        return "Final Answer", llm_output.split(FINAL_ANSWER_ACTION)[-1].strip()
     regex = r"Action: (.*?)\nAction Input: (.*)"
     match = re.search(regex, llm_output)
     if not match:

tests/unit_tests/agents/test_mrkl.py

@@ -34,6 +34,21 @@ def test_get_final_answer() -> None:
     assert action_input == "1994"
 
 
+def test_get_final_answer_new_line() -> None:
+    """Test getting final answer."""
+    llm_output = (
+        "Thought: I need to search for NBA\n"
+        "Action: Search\n"
+        "Action Input: NBA\n"
+        "Observation: founded in 1994\n"
+        "Thought: I can now answer the question\n"
+        "Final Answer:\n1994"
+    )
+    action, action_input = get_action_and_input(llm_output)
+    assert action == "Final Answer"
+    assert action_input == "1994"
+
+
 def test_get_final_answer_multiline() -> None:
     """Test getting final answer that is multiline."""
     llm_output = (