Exercises: PET SIMULATOR

Define class Pet:. Give it def __init__(self, name): and set self.name = name, self.hunger = 5, and self.happiness = 5. Make buddy = Pet("Buddy"), then print buddy.name and buddy.hunger.

Define the Pet class again with the same __init__ method and three attributes. Make two pets with different names. Use a while loop to lower only the first pet's hunger by 1 until it reaches 2. Then print both names and both hunger values. Your result should show that each object carries its own attributes.

Define the Pet class again with its __init__ method. Inside the class, add def feed(self, amount):. Make it change hunger with self.hunger = self.hunger - amount, then return the new hunger. Make Buddy, call buddy.feed(2), and print the returned value.

Define Pet with the same three starting attributes. Add def status(self): and create a variable named mood inside it. If hunger is greater than 6, use "hungry". Else if hunger is less than 3, use "stuffed". Otherwise, use "content". Finish the method by printing an f-string with the pet's name, mood, hunger, and happiness, then return mood. Make a pet, change its hunger to 8, and print what its status method returns (it should be "hungry").

Define Pet with __init__ and the full status mood ladder from Exercise 4. Start with pets = [], then append five new Pet objects. Use one for pet in pets: loop and call pet.status() once for each pet. After the loop, write and run these two lines yourself: print(pets[0].name) and pets[1].status().

Define Pet with __init__ and feed. Make two different food dictionaries: meals = {"apple": 2, "steak": 4} and treats = {"biscuit": 1, "carrot": 2}. Add a third entry, "fish": 3, to treats. Make Buddy, feed Buddy once from meals and once from treats, then print Buddy's hunger and the value stored for "fish".

In the regular code cell, define Pet with __init__, use the fixed name "Mochi", and make a pet. Use a while loop to add 1 to its happiness until happiness reaches 8, then print its name and happiness.

Run the next code cell yourself. Its last line has a spelling mistake, so Python will raise an AttributeError. Read the traceback from the bottom upward and find the misspelled attribute name.

Your traceback: Edit this markdown cell and replace this sentence with the traceback you saw.

Now write the corrected line in the following code cell and print the happiness value.

More Practice

Use Exercises 9–11 for homework or another practice session.

In the regular cell, define Pet with __init__ and feed, using five fixed pet names so the cell runs without waiting. Make a food dictionary and an empty pets list. Append five pets, then use a for pet in pets: loop to feed each pet from the dictionary. After the loop, print every pet's hunger with a second for pet in pets: loop.

Define Pet with __init__ and feed. Make a snack dictionary and one pet. Set stops = 0, then use a while stops < 3: loop. Each time through the loop, feed the pet from the snack dictionary and add 1 to stops. After the loop, print the pet's hunger and stops.

Define Pet with __init__ and the full status mood ladder. The method must use if/elif/else, choose a mood, and print an f-string with the pet's name and mood. Start with an empty pets list and append five pets. Use list indexes to set the first pet's hunger to 8 and the second pet's hunger to 1. Use a for pet in pets: loop to call status() for every pet, then print pets[4].name. The three pets after indexes 0 and 1 stay at the default hunger of 5.

In-Class Finale

In the regular cell, use the fixed name "Buddy" so the whole pet day runs without waiting. Define the full Pet class with __init__ and all four methods: feed, play, pass_time, and status. Use the same rules as the lesson: hunger and happiness start at 5; feed subtracts an amount from hunger; play adds 1 to happiness; pass_time adds 2 to hunger; and status uses the three-part mood ladder and prints an f-string. Make Buddy and call the methods in this exact order: feed(2), play(), pass_time(), status(). Finally, print Buddy's hunger and happiness. The final printed numbers should be 5 and 6. Use print to check your work; do not write an assert.

Start with a list named pets that holds several pets with different happiness values. Set best_pet = pets[0] and best = pets[0].happiness. Use one for pet in pets: loop. Inside it, compare with if pet.happiness > best:. When a pet has a new best happiness, update both best = pet.happiness and best_pet = pet. After the loop, print both best_pet.name and best.

Pattern Spotlight retrieval: Which pattern remembers WHO owns the best value? Variation axis — data shape: objects and their attributes, keeping the pet itself, instead of the earlier number-only file score.

Define Pet with __init__ and a play method that adds 1 to self.happiness. Make buddy = Pet("Buddy"). Use while buddy.happiness < 10: to call buddy.play(). After the loop, print Buddy's happiness.

Pattern Spotlight: which pattern is this? which variable/condition says 'done yet?' Variation — data type and packaging: an object method changes an attribute until it reaches the boundary, unlike the earlier inline number and string loops.

Define Pet with __init__(self, name, happiness) that stores both attributes. Use pets = [Pet("Mochi", 6), Pet("Sunny", 7), Pet("Pip", 9), Pet("Coco", 4)]. Set happiness_threshold = 7 and start a NEW empty list named happy_pets. Loop over pets. Inside the loop, use a condition to check whether each pet's happiness is at least the threshold, and append only passing pet objects to happy_pets. After the loop, use a second loop to print the name of every pet in the new list. The exact printed names should be Sunny and then Pip, one per line. Do not use a list comprehension.

Pattern Spotlight retrieval: Which pattern builds a new list containing only items that pass a test? Variation axis — pet objects and attributes: filter objects by their happiness attribute, then print their names.

Define a tiny Pet class whose __init__ stores only a hunger attribute. Make your own inline list named pets containing four Pet objects with hunger values 8, 3, 7, and 5, in that order. Use for pet in pets: to count how many pets have hunger greater than 6, then report the count.

Worked example: For these four pets, the answer is 2.

Define a tiny Pet class whose __init__ stores only a hunger attribute. Make your own inline list named pets containing four Pet objects with hunger values 8, 3, 7, and 5, in that order. Start a total at zero, use for pet in pets: to add every hunger value with long-form accumulation, and report the total. Use a loop rather than a built-in total shortcut.

Worked example: The four hunger values produce a total of 23.

Define a tiny Pet class whose __init__ stores only a name attribute. Make your own inline list named pets containing Pet objects named "Rex", "Mia", and "Sam", in that order. Search for "Mia" with for pet in pets:. Start a found flag as false; when the name matches, set the flag to true and break out of the loop. Report whether the name was found.

Worked example: The result is found = True.

Define a tiny Pet class whose __init__ stores only a name attribute. Make your own inline list named pets containing Pet objects named "Rex", "Mia", and "Sam", in that order. Start a NEW empty list, use for pet in pets: to append each pet's name, and report the completed names list.

Worked example: The result is ["Rex", "Mia", "Sam"].

Define a tiny Pet class whose __init__ stores only name and hunger. Make your own inline list named pets containing Pet("Rex", 8), Pet("Mia", 3), and Pet("Sam", 7), in that order. Seed BOTH the hungriest and least-hungry trackers from the first pet by using list indexing, not zero or a made-up large value. Then use for pet in pets: to scan the objects, update each tracker when needed, and report both pets' names and hunger values.

Worked example: The hungriest pet is "Rex" with hunger 8, and the least-hungry pet is "Mia" with hunger 3.

Define a tiny Pet class whose __init__ stores only a mood attribute. Make your own inline list named pets containing four Pet objects with moods "happy", "sad", "happy", and "hungry", in that order. Start an empty dictionary named counts. Use for pet in pets: and the pattern counts[mood] = counts.get(mood, 0) + 1 to tally the moods, then report the dictionary.

Worked example: The result is {"happy": 2, "sad": 1, "hungry": 1}.

Define a tiny Pet class whose __init__ stores only name and hunger. Make one Pet named Buddy with hunger 8. Make the snack sequence 2, 4, 3, 5, in that order. Hunger has a floor of 0. Move through the snacks in order with a single loop and check before feeding. Apply a snack only if subtracting it would leave hunger at or above zero. Otherwise, break immediately without applying that snack or any later snack. Use long-form subtraction and report Buddy's final hunger and the number of snacks used.

Paired contrast: This mirrors Exercise 23, but here you check the boundary before changing hunger, so the pet never goes below zero.

Worked example: Buddy goes 8 → 6 → 2. The next snack would change hunger by -3 and produce -1, so feeding stops before that snack. The final hunger is 2, and 2 snacks were used.

Define a tiny Pet class whose __init__ stores only name and hunger. Make one Pet named Buddy with hunger 8. Make the snack sequence 2, 4, 3, 5, in that order. Move through the snacks in order with a single loop and feed then check. Subtract each snack first, count it as used, and then break as soon as hunger is below zero. Start tipping_snack = 0 before the loop. Use long-form subtraction and report Buddy's final negative hunger, the number of snacks used, and the snack value that tipped hunger below zero.

Paired contrast: This mirrors Exercise 22, but here you change hunger before checking the boundary, so the result records the first step below zero.

Worked example: Buddy goes 8 → 6 → 2 → -1. The final hunger is -1, 3 snacks were used, and the tipping snack was 3.

Define a tiny Pet class whose __init__ stores only a hunger attribute. Make your own inline list named pets containing four Pet objects with hunger values 8, 3, 7, and 5, in that order. Use for pet in pets:. For each pet whose hunger is greater than 6, reduce that pet's hunger by 5 with long-form subtraction; leave pets with hunger 6 or below unchanged. Build and report a list of the resulting hunger values in the original order.

Worked example: The resulting hunger list is [3, 3, 2, 5].

Define Pet with __init__(self, name, trick) that stores both attributes and a show_trick method that prints an f-string describing the pet performing its trick. Make a list of at least three pets with different tricks. Use one for loop to call each pet's show_trick method.

Define Pet with __init__(self, name) that stores the name and starts hunger at 5, plus a feed(self, amount) method that lowers hunger. Make a foods dictionary and a list of at least three pets. Feed each pet a food amount from the dictionary, then use one for pet in pets: loop to print each pet's name and hunger in an f-string.