P ython p rogramming e xercises

Exercise #18: Buy 8 Get 1 Free 
def getCostOfCoffee(numberOfCoffees, pricePerCoffee): 
# Track the total price: 
totalPrice = 0 
# Track how many coffees we have until we get a free one: 
cupsUntilFreeCoffee = 8 
# Loop until the number of coffees to buy reaches 0: 
while numberOfCoffees > 0: 
# Decrement the number of coffees left to buy: 
numberOfCoffees -= 1 
# If this cup of coffee is free, reset the number to buy until 
# a free cup back to 8: 
if cupsUntilFreeCoffee == 0: 

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Python Programming Exercises, Gently Explained 
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cupsUntilFreeCoffee = 8 
# Otherwise, pay for a cup of coffee: 
else: 
# Increase the total price: 
totalPrice += pricePerCoffee 
# Decrement the coffees left until we get a free coffee: 
cupsUntilFreeCoffee -= 1 
# Return the total price: 
return totalPrice 
Alternate Solution: 
def getCostOfCoffee(numberOfCoffees, pricePerCoffee): 
# Calculate the number of free coffees we get in this order: 
numberOfFreeCoffees = numberOfCoffees // 9 
# Calculate the number of coffees we will have to pay for in this order: 
numberOfPaidCoffees = numberOfCoffees - numberOfFreeCoffees 
# Calculate and return the price: 
return numberOfPaidCoffees * pricePerCoffee 
Exercise #19: Password Generator 
# Import the random module for its randint() function. 
import random 
# Create string constants that for each type of character: 
LOWER_LETTERS = 'abcdefghijklmnopqrstuvwxyz' 
UPPER_LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' 
NUMBERS = '1234567890' 
SPECIAL = '~!@#$%^&*()_+' 
# Create a string with all of these strings combined: 
ALL_CHARS = LOWER_LETTERS + UPPER_LETTERS + NUMBERS + SPECIAL 
def generatePassword(length): 
# 12 is the minimum length for passwords: 
if length < 12: 
length = 12 
# Create a password variable that starts as an empty list: 
password = [] 
# Add a random character from the lowercase, uppercase, digits, and 
# punctuation character strings: 
password.append(LOWER_LETTERS[random.randint(0, 25)]) 
password.append(UPPER_LETTERS[random.randint(0, 25)]) 
password.append(NUMBERS[random.randint(0, 9)]) 
password.append(SPECIAL[random.randint(0, 12)]) 
# Keep adding random characters from the combined string until the 
# password meets the length: 
while len(password) < length: 
password.append(ALL_CHARS[random.randint(0, 74)]) 
# Randomly shuffle the password list: 

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Python Programming Exercises, Gently Explained 
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random.shuffle(password) 
# Join all the strings in the password list into one string to return: 
return ''.join(password)