Question

Pretty new to python/programming in general, this is my biggest project yet.

I am writing a program that will do SUVAT equations for you. (SUVAT equations are used to find the displacement, start/end velocity, acceleration and time travelled by an object with constant velocity, you may call them something different.)

I made this list:

variables = ["Displacement", "Start Velocity", "End Velocity", "Acceleration", "Time"]

which is used in the following while/for loop:

a = 0
while a==0:
  for variable in variables:

    # choice1 is what the user is looking to calculate
    choice1 = raw_input("Welcome to Mattin's SVUVAT Simulator! Choose the value you are trying to find. You can pick from " + str(variables))

    # will execute the following code when the for loop reaches an item that matches the raw_input
    if choice1 == variable: 
        print "You chave chosen", choice1
        variables.remove(variable) #Removes the chosen variable from the list, so the new list can be used later on
        a = 1 # Ends the for loop by making the while loop false

    # This part is so that the error message will not show when the raw_input does not match with the 4 items in the list the user has not chosen
    else:
        if choice1 == "Displacement":
            pass
        elif choice1 == "Start Velocity":
            pass
        elif choice1 == "End Velocity":
            pass
        elif choice1 == "Acceleration":
            pass

        # This error message will show if the input did not match any item in the list
        else:
            print "Sorry, I didn't understand that, try again. Make sure your spelling is correct (Case Sensitive), and that you did not inlcude the quotation marks."

Hopefully the comments I have written in the code should explain my intentions, if not, feel free to ask anything.

The problem is that when I run the code, and input choice1, the for loop activates the last line of code:

else:
    print "Sorry, I didn't understand that, try again. Make sure your spelling is correct (Case Sensitive), and that you did not inlcude the quotation marks."

and then prompts me to enter the input again, and will do this as many times as it needs to get to the item on the list that I am typing.

However, I specifically coded that if what I input does not match the item on the list the for loop is currently checking, but does match one of the other items on the list, then it should pass and loop round to checking the next item.

I am probably doing something stupid, but I don’t see it, so please help me figure out what I have to do to get my desired result? I assumed it was the syntax I had wrong so that is why that is the title.

Thanks for any help, I appreciate it.

Answer 1

Besides the problem with the indentation in your pasted code, I would rewrite it as such:

while True:
    choice = raw_input('...')

    if choice in variables:
        print "You chave chosen", choice

        # Remove the chosen member from the list
        variables = [v for v in variables if v != choice]

        # Break out of loop
        break

    # Print error messages etc.

Also remember that string comparisons are case sensitive. I.e 'Displacement' != 'displacement'.