Can I test a function defined in a file manually in the terminal in vscode?

I have previously only written python code using IDLE but since I am starting to do some more "heavier" programming I figured I should start using Visual Studio Code. I am however having issues doing things that I would like to do while coding to check that my functions are working as intended. The major thing I want to be able to do is if I have saved
def summa(x, y)
return x+y
in a file 'sum.py', then I would want to test run summa(3, 4) in the terminal. In IDLE I am used to just running the file containing the function and then use it but I cannot figure out how to do that in Visual Studio Code. However, I realize that it is possible to import the file into a REPL terminal but I would hope that there is some easier way of doing it.