How to loop back to the beginning of a programme - Python

Question

I've written a BMI calculator in python 3.4 and at the end I'd like to ask whether the user would like to use the calculator again and if yes go back to the beginning of the code. I've got this so far. Any help is very welcome :-)

#Asks if the user would like to use the calculator again
again =input("Thank you again for using this calculator, would you like to try again? Please type y for yes or n for no-")

while(again != "n") and (again != "y"):
    again =input("Please type a valid response. Would you like to try again? Please type y for yes or n for no-")

if again == "n" :
    print("Thank you, bye!")

elif again == "y" :

....

score 5 · Accepted Answer · answered Jan 31 '15 at 18:07

5

Wrap the whole code into a loop:

while True:

indenting every other line by 4 characters.

Whenever you want to "restart from the beginning", use statement

continue

Whenever you want to terminate the loop and proceed after it, use

break

If you want to terminate the whole program, import sys at the start of your code (before the while True: -- no use repeating the import!-) and whenever you want to terminate the program, use

sys.exit()

answered Jan 31 '15 at 18:07

Alex Martelli

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Where should I put the initial while true? where I want it to go back to? – nitrogirl Jan 31 '15 at 18:15
@nitrogirl, exactly -- presumably just after `import` statements or other initialization that you *don't* want to repeat over and over. – Alex Martelli Jan 31 '15 at 18:38

Padraic Cunningham · Answer 2 · 2015-01-31T18:16:21.167

You just need to call the function if the user wants to start again:

def calculate():
    # do work
    return play_again()


def play_again():
    while True:
        again = input("Thank you again for using this calculator, would you like to try again? Please type y for yes or n for no-")
        if again not in {"y","n"}:
            print("please enter valid input")               
        elif again == "n":
            return "Thank you, bye!"
        elif again == "y":
            # call function to start the calc again
            return calculate()
calculate()

How to loop back to the beginning of a programme - Python

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