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pythonfastapivisual-studio-2022uvicorn

VS 2022 Python - How to get going with FastAPI

I am using Visual Studio 2022 on Win11, and trying to get to grips with Python. In particular, I am trying out FastAPI.

I have installed FastAPI and Uvicorn. I have a virtual environment set up for Python 3.9.

How do I get VS to run the Uvicorn server when testing? I am trying to follow the start up guide (https://fastapi.tiangolo.com/tutorial/first-steps/). I have created a main.py file, with the required code. When I try to run it from an interactive console, I type uvicorn -m main:app --reload.

The console comes back with

File "stdin", line 1
    uvicorn -m main:app --reload
               ^
SyntaxError: invalid syntax

I have tried moving the example code to another file and trying to get uvicorn to run that file, but no joy. I think either uvicorn is not running, or the environment cannot find either uvicorn or the target main.py file.

I have tried running a DOS prompt, executing the python.exe in the venv folder, and trying to point to uvicorn directly...

"C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python39_64\python" -m "C:\Users\User\Documents\Visual Studio 2022\Repos\PythonApplicationFastAPITest1\env\Scripts\uvicorn" main:app --reload

...and I get "No module named ...uvicorn".

Solution

  • I got this working with MKrieger1's engagement.

    Uvicorn is a self contained app, uvicorn.exe, a server. I was trying to start it in a Python interpreter session, which was failing.

    I got it working by running uvicorn in an external DOS prompt. I referenced the uvicorn.exe that had been installed with the FastAPI package. The -m switch did not seem to work.

    When in DOS, I changed directory to the project folder holding my main.py file. I then issued the command...

    .\env\scripts\uvicorn main:app --reload

    ...and this started uvicorn.exe, found main.py, app object, and ran it. I was then able to browse to 127.0.0.1:8000 and get my "Hello, world" achievement.

    INFO:     Will watch for changes in these directories: ['C:\\Users\\User\\Documents\\Visual Studio 2022\\Repos\\PythonApplicationFastAPITest1']
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [23000] using WatchFiles
INFO:     Started server process [20528]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     127.0.0.1:49891 - "GET / HTTP/1.1" 200 OK