From the code you posted, there is no function call to vendingMachine()
Try at the top of your code:
print ("hello")
vendingMachine()
def vendingMachine():
...
Answer:
The correct syntax (assuming WinForms) is
lblMessage.Text = "Welcome to fiji";
The given statement fails to follow the syntax of literal strings, which should be in quotation marks. (depending on the framework and programming language, the txt property may also be incorrect, as well as the missing semi-colon).