Nested structures question

Discussion in 'Python' started by Physics Python, Jan 12, 2011.

  1. Hello,

    I am teaching myself python using the book: Python Programming for Absolute Beginners, 2nd edition by Michael Dawson. I am using python 2.7.1.

    In chapter 3 we are learning to use structures (while, if, elif) to write a program that has the user guess a number between 1 and 100.

    Here is the code for the baseline program:

    ------------- start --------------

    # Guess My Number
    #
    # The computer picks a random number between 1 and 100
    # The player tries to guess it and the computer lets
    # the player know if the guess is too high, too low
    # or right on the money

    import random

    print "\tWelcome to 'Guess My Number'!"
    print "\nI'm thinking of a number between 1 and 100."
    print "Try to guess it in as few attempts as possible.\n"

    # set the initial values
    the_number = random.randrange(100) + 1
    guess = int(raw_input("Take a guess: "))
    tries = 1

    # guessing loop
    while (guess != the_number):
    if (guess > the_number):
    print "Lower..."
    else:
    print "Higher..."

    guess = int(raw_input("Take a guess: "))
    tries += 1

    print "You guessed it! The number was", the_number
    print "And it only took you", tries, "tries!\n"

    raw_input("\n\nPress the enter key to exit.")

    ------------------- end ---------------------

    The book asks to write a version of this program that limits the number of guess the user can take. I have tried to write this program, and I am getting some run time errors. Can anybody take a look at my code and give me some advice or hints?

    Thanks!

    ---- start ---

    # Number Guessing Game Version 2
    #
    # The computer picks a random number between 1 and 100
    # The player tries to guess and the computer tells
    # the player if the guess is high or low or correct
    # The player has to guess the number in less than 7 tries.
    #
    # 1/12/2011



    import random

    # welcome the player to the game

    print "\tWelcome to 'Guess My Number'!"
    print "\nI am thinking of a number between 1 and 100."
    print "Try and guess it in as few attempts as possible.\n"

    # Set the initial values

    the_number= random.randrange(100) + 1
    guess = int(raw_input("Take a guess: "))
    tries = 1

    # Guessing loop


    while guess != the_number:
    while tries > 7:
    if guess > the_number:
    print "Lower..."
    else:
    print "Higher..."
    guess = int(raw_input("Take a guess: "))
    tries += 1

    print "You guessed it! The number was: ", the_number
    print "And it only took you", tries, "tries!\n"

    print "Wow, you suck at this, you should be able to solve this in 7 attempts or less"

    raw_input("Press Enter to exit the program.")

    ------- end -----
     
    Physics Python, Jan 12, 2011
    #1
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  2. Physics Python

    Tim Harig Guest

    On 2011-01-12, Physics Python <> wrote:
    > while guess != the_number:


    =================================================
    > while tries > 7:
    > if guess > the_number:
    > print "Lower..."
    > else:
    > print "Higher..."
    > guess = int(raw_input("Take a guess: "))
    > tries += 1

    =================================================

    Think about what happens when this nested loop exits because tries > 7? It
    returns to the outer loop whether or not the actual number was guessed
    correctly. There is no real need for this loop.

    > print "You guessed it! The number was: ", the_number
    > print "And it only took you", tries, "tries!\n"


    Note that the outer loop ends here without any test to see whether or not
    the number was actually guested and there is *nothing* that stops this
    outer loop, so it will spin forever.

    > print "Wow, you suck at this, you should be able to solve this in 7 attempts or less"
    >
    > raw_input("Press Enter to exit the program.")


    This is never reached.
     
    Tim Harig, Jan 12, 2011
    #2
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  3. Physics Python

    DevPlayer Guest

    looping = True
    while looping:
    guess = int(raw_input("Take a guess: "))
    tries += 1
    if guess > the_number:
    print "Lower..."
    elif guess < the_number:
    print "Higher..."
    else:
    print "You guessed it! The number was", the_number
    print "And it only took you", tries, "tries!\n"
    break

    if tries >= 7:
    print "Wow you suck! It should only take at most 7 tries!"
    looping = False


    # Alternatively while learing while looping use the continue statement

    looping = True
    while looping:
    guess = int(raw_input("Take a guess: "))
    tries += 1

    if guess > the_number:
    print "Lower..."
    elif guess < the_number:
    print "Higher..."
    else:
    print "You guessed it! The number was", the_number
    print "And it only took you", tries, "tries!\n"
    break

    if tries < 7:
    continue

    print "Wow you suck! It should only take at most 7 tries!"
    looping = False




    # In a while loop I recommend to NOT end loops using the
    # conditional test of == but instead use >, <, >= or <= or !=.
    # In a complex while loop the exit condition may be skipped
    # by mistake and you'll loop forever.

    # In while loops I get less bugs by putting the incrementor as
    # the last statement in the while block;
    # this helps follow precedence like range(7) is - zero to 6
    # as well as index 0 in a list is the first item. However
    # while index: where index == 0 will exit the loop before
    # it even starts as 0 == False (0 is not False but equals False)

    # Use the while loop for looping an undetermined number of
    # iterations or conditional iterations.
    # Use for loops for an explicid number of iterations.

    for tries in range(7):
    guess = int(raw_input("Take a guess: "))
    if guess > the_number:
    print "Lower..."
    elif guess < the_number:
    print "Higher..."
    else:
    print "You guessed it! The number was", the_number
    print "And it only took you", tries, "tries!\n"
    break
    if tries >= 7:
    print "Wow you suck! It should only take at most 7 tries!"

    # I'm guessing the chapter's test is to see if you remember the for
    loop.

    # start using print() to get into a good habit for Python 3.0+


    # I haven't seen the book but often one part of while that is
    # left off in tutorials is the "else" statement.
    while condition:
    "block"
    else:
    "block"

    # you can use else for when the condition never happens.
     
    DevPlayer, Jan 13, 2011
    #3
  4. Physics Python wrote:
    > Hello,
    >
    > I am teaching myself python using the book: Python Programming for Absolute Beginners, 2nd edition by Michael Dawson. I am using python 2.7.1.
    >
    > In chapter 3 we are learning to use structures (while, if, elif) to write a program that has the user guess a number between 1 and 100.
    >
    > Here is the code for the baseline program:
    >
    >

    [snip]

    here is an example of code using a for loop, which is always better than
    a while loop, when applicable of course.
    It uses the for... else... statement which is rather strange at first
    glance but has some uses, it's always good to know it exists.

    http://paste.pocoo.org/show/319931/

    JM
     
    Jean-Michel Pichavant, Jan 13, 2011
    #4
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