ModuleNotFoundError no module name 'httpx'

[VianneyMI]

Describe the bug
A clear and concise description of what the bug is.

Following the client tutorial, I am trying to launch the client with the weather server previously developed and I get this ModuleNotFoundError : No module name 'httpx'

Is it because I created separated virtual environments for the clients and the servers ?

Anyway, I have httpx installed in both.

How does the client process the provided server ? Do I need to launch the server manually first ?

Below is my project structure

model_context_protocol/

┣ mcp_client/
┃ ┣ .venv/
┃ ┣ .env
┃ ┣ .gitignore
┃ ┣ .python-version
┃ ┣ client.py
┃ ┣ pyproject.toml
┃ ┣ README.md
┃ ┗ uv.lock
┗ weather/
  ┣ .venv/
  ┣ .python-version
  ┣ pyproject.toml
  ┣ README.md
  ┣ uv.lock
  ┗ weather.py

[BoBo-Ye]

Oh, I know. There's one line in client.py: command = "python" if is_python else "node".
The logic behind it is to execute this command with anyio.open_process, if you just use python, then it will use the system's default python interpreter, not the virtual environment you created.
The true code is: command = "<YOUR_VENV_PATH>\\.venv\\Scripts\\python.exe" if is_python else "node".

[sterankin]

is this the reason my client fails with:

  File "/Users/me/src/quickstart-resources/weather-server-python/weather.py", line 3, in <module>
    from mcp.server.fastmcp import FastMCP
ModuleNotFoundError: No module named 'mcp.server.fastmcp'

even though its installed in the server?

what should YOUR_VENV_PATH be? I tried this:

command = "/Users/me/src/quickstart-resources/mcp-client-python/.venv/bin/python3.10" if is_python else "node"

I still get:

   from mcp.server.fastmcp import FastMCP
ModuleNotFoundError: No module named 'mcp.server.fastmcp'

[VianneyMI]

Oh, I know. There's one line in client.py: command = "python" if is_python else "node". The logic behind it is to execute this command with anyio.open_process, if you just use python, then it will use the system's default python interpreter, not the virtual environment you created. The true code is: command = "<YOUR_VENV_PATH>\\.venv\\Scripts\\python.exe" if is_python else "node".

Thanks, this did solve my initial issue. Now I have a new one (the client hangs forever)

[VianneyMI]

is this the reason my client fails with:

  File "/Users/me/src/quickstart-resources/weather-server-python/weather.py", line 3, in <module>
    from mcp.server.fastmcp import FastMCP
ModuleNotFoundError: No module named 'mcp.server.fastmcp'

even though its installed in the server?

what should YOUR_VENV_PATH be? I tried this:

command = "/Users/me/src/quickstart-resources/mcp-client-python/.venv/bin/python3.10" if is_python else "node"

I still get:

   from mcp.server.fastmcp import FastMCP
ModuleNotFoundError: No module named 'mcp.server.fastmcp'

Try to use relative paths instead

[sterankin]

Oh, I know. There's one line in client.py: command = "python" if is_python else "node". The logic behind it is to execute this command with anyio.open_process, if you just use python, then it will use the system's default python interpreter, not the virtual environment you created. The true code is: command = "<YOUR_VENV_PATH>\\.venv\\Scripts\\python.exe" if is_python else "node".

Should this path be to the client or the server venv?

[BoBo-Ye]

Oh, I know. There's one line in client.py: command = "python" if is_python else "node". The logic behind it is to execute this command with anyio.open_process, if you just use python, then it will use the system's default python interpreter, not the virtual environment you created. The true code is: command = "<YOUR_VENV_PATH>\\.venv\\Scripts\\python.exe" if is_python else "node".

Should this path be to the client or the server venv?

I don't think that's why it happened to you. You may search your virtual python environment: .\.venv\Lib\site-packages\mcp\server\fastmcp and check whether this folder exists. If not, it should be the mcp version problem, you need to update to the latest version.