Nested structures question


P

Physics Python

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 -----
 
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T

Tim Harig

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.
 
D

DevPlayer

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.
 
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J

Jean-Michel Pichavant

Physics said:
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
 

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