Running into an `ImportError` when executing the MCP client in `examples/servers/simple-tool`

[Lando-Loeper-Neew-Ventures]

Initial Checks

• I confirm that I'm using the latest version of MCP Python SDK
• I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue

Description

I wanted to test my MCP server the same way in the examples/servers/simple-tool however running the MCP client script I run into:

ImportError: cannot import name 'ClientSession' from partially initialized module 'mcp.client.session' (mos│
t likely due to a circular import)

Any help appreciated

Example Code

import asyncio
from mcp.client.session import ClientSession
from mcp.client.stdio import StdioServerParameters, stdio_client


async def main():
    async with stdio_client(
        StdioServerParameters(command="uv", args=["run", "mcp-simple-tool"])
    ) as (read, write):
        async with ClientSession(read, write) as session:
            await session.initialize()

            # List available tools
            tools = await session.list_tools()
            print(tools)

            # Call the fetch tool
            result = await session.call_tool("fetch", {"url": "https://example.com"})
            print(result)


asyncio.run(main())

Python & MCP Python SDK

Python Version: 3.13.5
Python SDK: 1.10.1
uv: 0.7.19

[nusrathdev]

Sure your script is not named mcp.py or similar.
Place your script outside the src or mcp/ directories.
Double-check your import statements.
Clean your environment if needed.

[Lando-Loeper-Neew-Ventures]

It was the naming of the script. Thanks for pointing that out! However, I am a little baffled as the name was email.py and I have no idea with what that name might be clashing to cause this dependency error. I have no other file with that name in my project.

[nusrathdev]

glad to hear the naming fix resolved it! The reason “email.py” can cause issues is that pythoan’s standard library has a built-in module. If your script or module is named email.py, it can shadow the standard library’s email module, leading to confusing import errors or circular dependencies, even if you don’t have another local file with that name. Renaming avoids this conflict. It’s a common Python gotcha!