combine python files (#256)

langchain/python.py

@@ -1,4 +1,6 @@
 """Mock Python REPL."""
+import sys
+from io import StringIO
 from typing import Dict, Optional
 
 
@@ -10,6 +12,11 @@ class PythonREPL:
         self._globals = _globals if _globals is not None else {}
         self._locals = _locals if _locals is not None else {}
 
-    def run(self, command: str) -> None:
-        """Run command with own globals/locals."""
+    def run(self, command: str) -> str:
+        """Run command with own globals/locals and returns anything printed."""
+        old_stdout = sys.stdout
+        sys.stdout = mystdout = StringIO()
         exec(command, self._globals, self._locals)
+        sys.stdout = old_stdout
+        output = mystdout.getvalue()
+        return output