Improved query, print & exception handling in REPL Tool (#4997)

Update to pull request https://github.com/hwchase17/langchain/pull/3215

Summary:
1) Improved the sanitization of query (using regex), by removing python
command (since gpt-3.5-turbo sometimes assumes python console as a
terminal, and runs python command first which causes error). Also
sometimes 1 line python codes contain single backticks.
2) Added 7 new test cases.

For more details, view the previous pull request.

---------

Co-authored-by: Deepak S V <svdeepak99@users.noreply.github.com>

langchain/tools/python/tool.py

@@ -1,7 +1,9 @@
 """A tool for running python code in a REPL."""
 
 import ast
+import re
 import sys
+from contextlib import redirect_stdout
 from io import StringIO
 from typing import Any, Dict, Optional
 
@@ -19,14 +21,13 @@ def _get_default_python_repl() -> PythonREPL:
     return PythonREPL(_globals=globals(), _locals=None)
 
 
-_MD_PY_BLOCK = "```python"
-
-
 def sanitize_input(query: str) -> str:
-    query = query.strip()
-    if query[: len(_MD_PY_BLOCK)] == _MD_PY_BLOCK:
-        query = query[len(_MD_PY_BLOCK) :].strip()
-    query = query.strip("`").strip()
+    # Remove whitespace, backtick & python (if llm mistakes python console as terminal)
+
+    # Removes `, whitespace & python from start
+    query = re.sub(r"^(\s|`)*(?i:python)?\s*", "", query)
+    # Removes whitespace & ` from end
+    query = re.sub(r"(\s|`)*$", "", query)
     return query
 
 
@@ -101,19 +102,18 @@ class PythonAstREPLTool(BaseTool):
             exec(ast.unparse(module), self.globals, self.locals)  # type: ignore
             module_end = ast.Module(tree.body[-1:], type_ignores=[])
             module_end_str = ast.unparse(module_end)  # type: ignore
+            io_buffer = StringIO()
             try:
-                return eval(module_end_str, self.globals, self.locals)
+                with redirect_stdout(io_buffer):
+                    ret = eval(module_end_str, self.globals, self.locals)
+                    if ret is None:
+                        return io_buffer.getvalue()
+                    else:
+                        return ret
             except Exception:
-                old_stdout = sys.stdout
-                sys.stdout = mystdout = StringIO()
-                try:
+                with redirect_stdout(io_buffer):
                     exec(module_end_str, self.globals, self.locals)
-                    sys.stdout = old_stdout
-                    output = mystdout.getvalue()
-                except Exception as e:
-                    sys.stdout = old_stdout
-                    output = repr(e)
-                return output
+                return io_buffer.getvalue()
         except Exception as e:
             return "{}: {}".format(type(e).__name__, str(e))
 

tests/unit_tests/tools/python/test_python.py

@@ -1,6 +1,7 @@
 """Test Python REPL Tools."""
 import sys
 
+import numpy as np
 import pytest
 
 from langchain.tools.python.tool import (
@@ -17,6 +18,18 @@ def test_python_repl_tool_single_input() -> None:
     assert int(tool.run("print(1 + 1)").strip()) == 2
 
 
+def test_python_repl_print() -> None:
+    program = """
+import numpy as np
+v1 = np.array([1, 2, 3])
+v2 = np.array([4, 5, 6])
+dot_product = np.dot(v1, v2)
+print("The dot product is {:d}.".format(dot_product))
+    """
+    tool = PythonREPLTool()
+    assert tool.run(program) == "The dot product is 32.\n"
+
+
 @pytest.mark.skipif(
     sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
 )
@@ -27,6 +40,103 @@ def test_python_ast_repl_tool_single_input() -> None:
     assert tool.run("1 + 1") == 2
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
+)
+def test_python_ast_repl_return() -> None:
+    program = """
+```
+import numpy as np
+v1 = np.array([1, 2, 3])
+v2 = np.array([4, 5, 6])
+dot_product = np.dot(v1, v2)
+int(dot_product)
+```
+    """
+    tool = PythonAstREPLTool()
+    assert tool.run(program) == 32
+
+    program = """
+```python
+import numpy as np
+v1 = np.array([1, 2, 3])
+v2 = np.array([4, 5, 6])
+dot_product = np.dot(v1, v2)
+int(dot_product)
+```
+    """
+    assert tool.run(program) == 32
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
+)
+def test_python_ast_repl_print() -> None:
+    program = """python
+string = "racecar"
+if string == string[::-1]:
+    print(string, "is a palindrome")
+else:
+    print(string, "is not a palindrome")"""
+    tool = PythonAstREPLTool()
+    assert tool.run(program) == "racecar is a palindrome\n"
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
+)
+def test_repl_print_python_backticks() -> None:
+    program = "`print('`python` is a great language.')`"
+    tool = PythonAstREPLTool()
+    assert tool.run(program) == "`python` is a great language.\n"
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
+)
+def test_python_ast_repl_raise_exception() -> None:
+    data = {"Name": ["John", "Alice"], "Age": [30, 25]}
+    program = """
+import pandas as pd
+df = pd.DataFrame(data)
+df['Gender']
+    """
+    tool = PythonAstREPLTool(locals={"data": data})
+    expected_outputs = (
+        "KeyError: 'Gender'",
+        "ModuleNotFoundError: No module named 'pandas'",
+    )
+    assert tool.run(program) in expected_outputs
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
+)
+def test_python_ast_repl_one_line_print() -> None:
+    program = 'print("The square of {} is {:.2f}".format(3, 3**2))'
+    tool = PythonAstREPLTool()
+    assert tool.run(program) == "The square of 3 is 9.00\n"
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
+)
+def test_python_ast_repl_one_line_return() -> None:
+    arr = np.array([1, 2, 3, 4, 5])
+    tool = PythonAstREPLTool(locals={"arr": arr})
+    program = "`(arr**2).sum()   # Returns sum of squares`"
+    assert tool.run(program) == 55
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 9), reason="Requires python version >= 3.9 to run."
+)
+def test_python_ast_repl_one_line_exception() -> None:
+    program = "[1, 2, 3][4]"
+    tool = PythonAstREPLTool()
+    assert tool.run(program) == "IndexError: list index out of range"
+
+
 def test_sanitize_input() -> None:
     query = """
     ```