Python f-strings don't work like that. The expression is evaluated when the string constant is defined, not when it's used, so your scenario is "code execution leads to code execution".

  >>> def server(userdata):
  ...   print("Your data:", userdata)
  ... 
  >>> value = f"Printing... {print('Eval!')}"
  Eval!
  >>> server(value)
  Your data: Printing... None