WEEK03: booleans, conditionals (if/else)
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 W: review expressions, if/else, comparison operators

FUN:
http://en.wikipedia.org/wiki/George_Boole

CONDITIONAL STATEMENTS:

if < condition > :
  do this
  and this
  and anything indented to this level
else:
  do that
  and that


EXAMPLE:

  speed = input("\nHow fast were you going? ")

  if speed > 55:
    print "that's too fast....SLOW DOWN!!!!!!!!!!!!!"
    print "here's your ticket\n"
  else:
    print "OK...off you go.\n"


WRITE YOUR PROGRAMS IN STAGES!!

 - write a small part of your program, then test it
 - once it works, add another small part, then test it again
 - and so on...

Here's an example:

$ python multiply1.py 

Let's test your multiplication skills...
 
What is 3 x 7 ? 20
Incorrect....the answer was 21

$ python multiply1.py 

Let's test your multiplication skills...
 
What is 3 x 7 ? 21
CORRECT!!

 - this program always asks 3 x 7
 - not much fun yet, but let's get that to work, then add to it!

"""
program to test user multiplication skills
J. Knerr -- Fall 2012
"""

# ------------------------------------------------------ #

def main():
  """ask user question, give feedback on user answer"""

  print "\nLet's test your multiplication skills...\n "

  a = 3
  b = 7
  answer = a * b

  question = "What is %d x %d ? " % (a,b)
  useranswer = input(question)

  if useranswer == answer:
    print "CORRECT!!\n"
  else:
    print "Incorrect....the answer was %d\n" % (answer)

# ------------------------------------------------------ #
main()

 - note use of variables a, b, and answer
 - use variables!! makes code easy to read and more efficient
 - also can make code easy to update, like this:

$ python multiply2.py 

Let's test your multiplication skills...
 
Please enter a factor: 5
What is 5 x 7 ? 35
CORRECT!!

$ python multiply2.py 

Let's test your multiplication skills...
 
Please enter a factor: 6
What is 6 x 7 ? 42
CORRECT!!

 - now we are asking the user for a factor, then testing them
   on factor x 7
 - the only difference between this new code and the one above?

change   a = 3
to       a = input("Please enter a factor: ")

# --------------------------------------------------- #

ADD RANDOM NUMBERS TO YOUR PROGRAMS:

>>> from random import *
>>> x = randrange(1,11)
>>> print x
2
>>> x = randrange(1,11)
>>> print x
9
>>> x = randrange(1,11)
>>> print x
3
>>> 
>>> item = choice(["apple", "orange", "lemon"])
>>> print item
apple
>>> item = choice(["apple", "orange", "lemon"])
>>> print item
apple
>>> item = choice(["apple", "orange", "lemon"])
>>> print item
lemon
>>> item = choice(["apple", "orange", "lemon"])
>>> print item
orange

 - change the above multiply code to test the user on factor x random_number:

$ python multiply3.py 

Let's test your multiplication skills...
 
Please enter a factor: 5
What is 5 x 9 ? 45
CORRECT!!

$ python multiply3.py 

Let's test your multiplication skills...
 
Please enter a factor: 5
What is 5 x 5 ? 25
CORRECT!!

# --------------------------------------------------- #

 - now let's put this in a LOOP and ask the user 3 multiplication questions:

$ python multiply4.py 

Let's test your multiplication skills...
 
Please enter a factor: 5
What is 5 x 5 ? 25
CORRECT!!

What is 5 x 2 ? 10
CORRECT!!

What is 5 x 4 ? 20
CORRECT!!

# --------------------------------------------------- #

 - if you have time: keep track of how many they get correct and
   include a message at the end, based on how well they did:

$ python multiply5.py 

Let's test your multiplication skills...
 
Please enter a factor: 5
What is 5 x 10 ? 50
CORRECT!!

What is 5 x 2 ? 10
CORRECT!!

What is 5 x 5 ? 25
CORRECT!!

Excellent work!!


$ python multiply5.py 

Let's test your multiplication skills...
 
Please enter a factor: 5
What is 5 x 10 ? 1
Incorrect....the answer was 50

What is 5 x 4 ? 1
Incorrect....the answer was 20

What is 5 x 7 ? 1
Incorrect....the answer was 35

Not so good...you need to run the program again! :( 

# --------------------------------------------------- #

NOTE: for this last part you need if/elif/else branching:

  if nright == nprobs:
    print "Excellent work!!"
  elif nright > nprobs/2:
    print "Good job. Keep practicing!"
  else:
    print "Not so good...you need to run the program again! :( "