Python REPL MCP server

This MCP server provides a Python REPL (Read-Eval-Print Loop) that allows execution of Python code through the MCP protocol with a persistent session. It maintains your variables between executions, making it perfect for interactive Python development or exploration directly within Claude Desktop.

Installation

No special installation is required as the project uses uv for dependency management. Simply run the server with:

uv run src/python_repl/server.py

Configuration with Claude Desktop

To use this Python REPL with Claude Desktop, add the following configuration to your Claude Desktop config file:

{
  "mcpServers": {
    "python-repl": {
      "command": "uv",
      "args": [
        "--directory",
        "/absolute/path/to/python-repl-server",
        "run",
        "mcp_python"
      ]
    }
  }
}

Make sure to replace /absolute/path/to/python-repl-server with the actual path to your server directory.

Available Tools

Execute Python Code

The execute_python tool runs Python code while maintaining variables between executions:

• Parameters:
  • code: The Python code you want to execute
  • reset: Optional boolean to reset the session (clears all variables)

List Variables

The list_variables tool shows all variables currently defined in your session.

Install Packages

The install_package tool lets you install a Python package from PyPI:

• Parameters:
  • Package name to install

Usage Examples

Setting Variables

a = 42
b = "Hello, world!"
my_list = [1, 2, 3, 4]

Using Previously Set Variables

print(f"The value is {a}")
print(f"The list contains {len(my_list)} items")

Listing All Session Variables

Use the list_variables tool to see all variables currently defined in your session.

Resetting the Session

To clear all variables and start fresh, use the execute_python tool with the reset parameter set to true.

Installing a Package

To install a package like numpy, use the install_package tool.

How to install this MCP server

For Claude Code

To add this MCP server to Claude Code, run this command in your terminal:

claude mcp add-json "python-repl" '{"command":"uv","args":["--directory","/absolute/path/to/python-repl-server","run","mcp_python"]}'

See the official Claude Code MCP documentation for more details.

For Cursor

There are two ways to add an MCP server to Cursor. The most common way is to add the server globally in the ~/.cursor/mcp.json file so that it is available in all of your projects.

If you only need the server in a single project, you can add it to the project instead by creating or adding it to the .cursor/mcp.json file.

Adding an MCP server to Cursor globally

To add a global MCP server go to Cursor Settings > Tools & Integrations and click "New MCP Server".

When you click that button the ~/.cursor/mcp.json file will be opened and you can add your server like this:

{
    "mcpServers": {
        "python-repl": {
            "command": "uv",
            "args": [
                "--directory",
                "/absolute/path/to/python-repl-server",
                "run",
                "mcp_python"
            ]
        }
    }
}

Adding an MCP server to a project

To add an MCP server to a project you can create a new .cursor/mcp.json file or add it to the existing one. This will look exactly the same as the global MCP server example above.

How to use the MCP server

Once the server is installed, you might need to head back to Settings > MCP and click the refresh button.

The Cursor agent will then be able to see the available tools the added MCP server has available and will call them when it needs to.

You can also explicitly ask the agent to use the tool by mentioning the tool name and describing what the function does.

For Claude Desktop

To add this MCP server to Claude Desktop:

1. Find your configuration file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json
• Linux: ~/.config/Claude/claude_desktop_config.json

2. Add this to your configuration file:

{
    "mcpServers": {
        "python-repl": {
            "command": "uv",
            "args": [
                "--directory",
                "/absolute/path/to/python-repl-server",
                "run",
                "mcp_python"
            ]
        }
    }
}

3. Restart Claude Desktop for the changes to take effect