loops - Python: How to keep repeating a program until a specific input is obtained?

11
votes

I have a function that evaluates input, and I need to keep asking for their input and evaluating it until they enter a blank line. How can I set that up?

while input != '':
    evaluate input

I thought of using something like that, but it didn't exactly work. Any help?

4
pythonloopsfor-loopwhile-loop
How does it not work? What does it do? What do you expect to see? - Collin
That above code repeatedly asks for the input if it is not ''. I need it to evaluate input until a blank line is entered. - user3033494

4 Answers

25
votes

There are two ways to do this. First is like this:

while True:             # Loop continuously
    inp = raw_input()   # Get the input
    if inp == "":       # If it is a blank line...
        break           # ...break the loop

The second is like this:

inp = raw_input()       # Get the input
while inp != "":        # Loop until it is a blank line
    inp = raw_input()   # Get the input again

Note that if you are on Python 3.x, you will need to replace raw_input with input.

1
votes

you probably want to use a separate value that tracks if the input is valid:

good_input = None
while not good_input:
     user_input = raw_input("enter the right letter : ")
     if user_input in list_of_good_values: 
        good_input = user_input
1
votes

This is a small program that will keep asking an input until required input is given.

we should keep the required number as a string, otherwise it may not work. input is taken as string by default

required_number = '18'

while True:
    number = input("Enter the number\n")
    if number == required_number:
        print ("GOT IT")
        break
    else:
        print ("Wrong number try again")

or you can use eval(input()) method

required_number = 18

while True:
    number = eval(input("Enter the number\n"))
    if number == required_number:
        print ("GOT IT")
        break
    else:
        print ("Wrong number try again")
0
votes

Easier way:

#required_number = 18

required_number=input("Insert a number: ")
while required_number != 18
    print("Oops! Something is wrong")
    required_number=input("Try again: ")
if required_number == '18'
    print("That's right!")

#continue the code