##############

# Example of missing "global"

n1 = 0

def increment():

global n1

n1 = n1 + 1

increment()

increment()

increment()

print n1

##############

# Example of missing "global"

n2 = 0

def assign(x):

n2 = x

assign(2)

assign(15)

assign(7)

print n2

##############

# Example of missing "return"

n3 = 0

def decrement():

global n3

n3 = n3 - 1

x = decrement()

print "x = ", x

print "n = ", n3

##############

# Example of print debugging

import simplegui

x = 0

def f(n):

print "f: n,x = ", n, x

result = n ** x

print "f: result = ",result

return result

def button_handler():

global x

print "bh : x = ", x

x += 1

print "bh : x = ", x

def input_handler(text):

print "ih : text = ", text

print f(float(text))

frame = simplegui.create_frame("Example", 200, 200)

frame.add_button("Increment", button_handler)

frame.add_input("Number:", input_handler, 100)

frame.start()

##############

# Examples of simplifying conditionals

def f1(a, b):

"""Returns True exactly when a is False and b is True."""

if a == False and b == True:

return True

else:

return False

def f2(a, b):

"""Returns True exactly when a is False and b is True."""

if not a and b:

return True

else:

return False

def f3(a, b):

"""Returns True exactly when a is False and b is True."""

return not a and b

def g1(a, b):

"""Returns False eactly when a and b are both True."""

if a == True and b == True:

return False

else:

return True

def g2(a, b):

"""Returns False eactly when a and b are both True."""

if a and b:

return False

else:

return True

def g3(a, b):

"""Returns False eactly when a and b are both True."""

return not (a and b)