Return output of PythonAstREPLTool when falling back to exec() (#2780)

When the code ran by the PythonAstREPLTool contains multiple statements
it will fallback to exec() instead of using eval(). With this change, it
will also return the output of the code in the same way the
PythonREPLTool will.

langchain/tools/python/tool.py

@@ -2,6 +2,7 @@
 
 import ast
 import sys
+from io import StringIO
 from typing import Dict, Optional
 
 from pydantic import Field, root_validator
@@ -77,8 +78,16 @@ class PythonAstREPLTool(BaseTool):
             try:
                 return eval(module_end_str, self.globals, self.locals)
             except Exception:
-                exec(module_end_str, self.globals, self.locals)
-                return ""
+                old_stdout = sys.stdout
+                sys.stdout = mystdout = StringIO()
+                try:
+                    exec(module_end_str, self.globals, self.locals)
+                    sys.stdout = old_stdout
+                    output = mystdout.getvalue()
+                except Exception as e:
+                    sys.stdout = old_stdout
+                    output = str(e)
+                return output
         except Exception as e:
             return str(e)