Loop until a specific user input [duplicate]

Question

I am trying to write a number guessing program as follows:

def oracle():
    n = ' '
    print 'Start number = 50'
    guess = 50 #Sets 50 as a starting number
    n = raw_input("\n\nTrue, False or Correct?: ")
    while True:
        if n == 'True':
            guess = guess + int(guess/5)
            print
            print 'What about',guess, '?'
            break
        elif n == 'False':
            guess = guess - int(guess/5)
            print
            print 'What about',guess, '?'
            break
        elif n == 'Correct':
            print 'Success!, your number is approximately equal to:', guess

oracle()

What I am trying to do now is get this sequence of if/ elif/ else commands to loop until the user enters 'Correct', i.e. when the number stated by the program is approximately equal to the users number, however if I do not know the users number I cannot think how I could implement and if statement, and my attempts to use 'while' also do not work.

Fred Foo · Accepted Answer · 2011-11-13 20:24:17Z

19

As an alternative to @Mark Byers' approach, you can use while True:

guess = 50     # this should be outside the loop, I think
while True:    # infinite loop
    n = raw_input("\n\nTrue, False or Correct?: ")
    if n == "Correct":
        break  # stops the loop
    elif n == "True":
        # etc.

edited Nov 13, 2011 at 20:24

answered Nov 13, 2011 at 20:16

Fred Foo

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5 Comments

Mark Byers Over a year ago

+1 similar to my update. I think the use of input here is also wrong.

Fred Foo Over a year ago

@MarkByers: changed it to raw_input. From the looks of the print statements, the OP is using Python 2.

George Burrows Over a year ago

Could either of you tell me why the code now terminates after entering True or False?

Mark Byers Over a year ago

Err... perhaps because you put a break statement there?! What exactly did you think would happen when it hit the break statement? Perhaps you should read a Python tutorial...

George Burrows Over a year ago

Sorry I'm being stupid, I have been up for too long haha, thanks for the help :)

Mark Byers · Accepted Answer · 2011-11-13 20:18:43Z

2

Your code won't work because you haven't assigned anything to n before you first use it. Try this:

def oracle():
    n = None
    while n != 'Correct':
        # etc...

A more readable approach is to move the test until later and use a break:

def oracle():
    guess = 50

    while True:
        print 'Current number = {0}'.format(guess)
        n = raw_input("lower, higher or stop?: ")
        if n == 'stop':
            break
        # etc...

Also input in Python 2.x reads a line of input and then evaluates it. You want to use raw_input.

Note: In Python 3.x, raw_input has been renamed to input and the old input method no longer exists.

edited Nov 13, 2011 at 20:18

answered Nov 13, 2011 at 20:13

Mark Byers

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2 Comments

Fred Foo Over a year ago

+1, though it would be more pythonic to use None to denote "no value".

George Burrows Over a year ago

Could either of you tell me why the code now terminates after entering True or False?

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