P ython p rogramming e xercises

Exercise #30: 3D Box Drawing 
def drawBox(size): 
# Special case: Draw nothing if size is less than 1: 
if size < 1: 
return 
# Draw back line on top surface: 
print(' ' * (size + 1) + '+' + '-' * (size * 2) + '+') 
# Draw top surface: 
for i in range(size): 
print(' ' * (size - i) + '/' + ' ' * (size * 2) + '/' + ' ' * i + '|') 
# Draw top line on top surface: 
print('+' + '-' * (size * 2) + '+' + ' ' * size + '+') 
# Draw front surface: 
for i in range(size - 1, -1, -1): 
print('|' + ' ' * (size * 2) + '|' + ' ' * i + '/') 
# Draw bottom lie on front surface: 
print('+' + '-' * (size * 2) + '+') 
# In a loop, call drawBox() with arguments 1 to 5: 
for i in range(1, 6): 
drawBox(i) 
Exercise #31: Convert Integers to Strings 
def convertIntToStr(integerNum): 
# Special case: Check if integerNum is 0, and return '0' if so: 
if integerNum == 0: 
return '0' 

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Python Programming Exercises, Gently Explained 
146 
# This dictionary maps single integer digits to string digits: 
DIGITS_INT_TO_STR = {0: '0', 1: '1', 2: '2', 3: '3', 4: '4', 
5: '5', 6: '6', 7: '7', 8: '8', 9: '9'} 
# Make a note whether the number is negative or not, and make 
# integerNum positive for the rest of the function's code: 
if integerNum < 0: 
isNegative = True 
integerNum = -integerNum 
else: 
isNegative = False 
# stringNum holds the converted string, and starts off blank: 
stringNum = '' 
# Keeping looping while integerNum is greater than zero: 
while integerNum > 0: 
# Mod the integerNum by 10 to get the digit in the ones place: 
onesPlaceDigit = integerNum % 10 
# Put the corresponding string digit at the front of stringNum: 
stringNum = DIGITS_INT_TO_STR[onesPlaceDigit] + stringNum 
# Divide integerNum by ten to remove one entire digit place: 
integerNum //= 10 
# If the number was originally negative, add a minus sign: 
if isNegative: 
return '-' + stringNum 
else: 
return stringNum