Object lifecycle overview in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an object of class Person.

Python

class Person:
    def __init__(self, name):
        self.name = name

p = [1]("Alice")
print(p.name)

Drag options to blanks, or click blank then click option'

APerson

Bobject

Cself

Dinit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'object' instead of the class name.

Using 'self' outside the class.

Using 'init' which is a method name, not a class.

The correct way to create an object is by calling the class name like a function.

2fill in blank

medium

Complete the code to define a destructor method that prints a message when an object is deleted.

Python

class Car:
    def __del__(self):
        print([1])

c = Car()
del c

Drag options to blanks, or click blank then click option'

ACar object deleted

BCar object destroyed

C'Car object deleted'

D'Car object destroyed'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string message.

Using print without parentheses (Python 3 requires parentheses).

The destructor method __del__ should print a string message, so it must be in quotes.

3fill in blank

hard

Fix the error in the code to properly initialize the object with a name attribute.

Python

class Animal:
    def __init__(self, name):
        [1].name = name

pet = Animal("Buddy")
print(pet.name)

Drag options to blanks, or click blank then click option'

AAnimal

Bself

Cthis

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name instead of 'self'.

Using 'this' which is not a Python keyword.

Using the attribute name instead of 'self'.

Inside methods, 'self' refers to the current object and is used to set attributes.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps each word to its length only if the length is greater than 3.

Python

words = ["apple", "cat", "banana", "dog"]
lengths = {word: [1] for word in words if len(word) [2] 3}

Drag options to blanks, or click blank then click option'

Alen(word)

B>

C<

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in the condition.

Using 'word' instead of 'len(word)' for the value.

Not filtering words correctly.

The dictionary comprehension uses len(word) to get length and filters words with length greater than 3 using '>'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps uppercase keys to their values only if the value is greater than 0.

Python

data = {'a': 1, 'b': 0, 'c': 3}
result = { [1]: [2] for k, v in data.items() if v [3] 0 }

Drag options to blanks, or click blank then click option'

Ak.upper()

Bv

C>

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'k' instead of 'k.upper()' for keys.

Using '<' instead of '>' in the condition.

Using 'k' instead of 'v' for values.

The comprehension uses k.upper() as keys, v as values, and filters values greater than 0.

Practice

1. What is the first step in the lifecycle of a Python object?

easy

A. Creation of the object in memory

B. Deletion of the object

C. Garbage collection

D. Assignment of a variable

Solution

1. Step 1: Understand object lifecycle start

   The lifecycle of a Python object begins when it is created in memory.

2. Step 2: Differentiate from other lifecycle stages

   Deletion and garbage collection happen later, after creation and use.

3. Final Answer:

   Creation of the object in memory -> Option A

4. Quick Check:

   Object lifecycle starts with creation [OK]

Hint: Object lifecycle always starts with creation [OK]

Common Mistakes:

• Confusing creation with deletion
• Thinking garbage collection happens first
• Assuming variable assignment is the first step

2. Which of the following is the correct syntax to define a destructor method in a Python class?

easy

A. def destructor(self):

B. def __del__(self):

C. def delete(self):

D. def __destroy__(self):

Solution

1. Step 1: Recall destructor method name

   In Python, the destructor method is named __del__ with double underscores before and after.

2. Step 2: Check syntax correctness

   The correct syntax is def __del__(self): which matches Python's special method naming.

3. Final Answer:

   def __del__(self): -> Option B

4. Quick Check:

   Destructor method = __del__ [OK]

Hint: Destructor method is always named __del__ [OK]

Common Mistakes:

• Using wrong method names like destructor or delete
• Missing double underscores
• Confusing with constructor __init__

3. What will be the output of the following code?

class MyClass:
    def __init__(self):
        print('Created')
    def __del__(self):
        print('Deleted')

obj = MyClass()
print('Object in use')
del obj
print('End')

medium

A. Created\nObject in use\nDeleted\nEnd

B. Created\nDeleted\nObject in use\nEnd

C. Object in use\nCreated\nDeleted\nEnd

D. Created\nObject in use\nEnd

Solution

1. Step 1: Trace object creation and constructor call

   When obj = MyClass() runs, __init__ prints 'Created'.

2. Step 2: Follow print and deletion order

   Next, 'Object in use' prints. Then del obj calls __del__, printing 'Deleted'. Finally, 'End' prints.

3. Final Answer:

   Created\nObject in use\nDeleted\nEnd -> Option A

4. Quick Check:

   Constructor then prints, then destructor after del [OK]

Hint: Destructor runs only after del or object goes out of scope [OK]

Common Mistakes:

• Assuming destructor runs immediately after creation
• Ignoring order of print statements
• Thinking del obj skips destructor

4. Identify the error in this code related to object lifecycle:

class Sample:
    def __init__(self):
        print('Init called')
    def __del__(self):
        print('Del called')

obj = Sample()
obj = None
print('Done')

medium

A. Destructor __del__ will not be called because obj is set to None

B. Syntax error in class definition

C. No error; destructor will be called when obj is set to None

D. Constructor __init__ will not be called

Solution

1. Step 1: Understand what happens when obj is set to None

   Setting obj = None removes the reference to the Sample object, so it becomes eligible for garbage collection.

2. Step 2: Confirm destructor call behavior

   When no references remain, __del__ is called, so 'Del called' will print before 'Done'.

3. Final Answer:

   No error; destructor will be called when obj is set to None -> Option C

4. Quick Check:

   Destructor runs when object has no references [OK]

Hint: Destructor runs when last reference is removed [OK]

Common Mistakes:

• Thinking setting variable to None skips destructor
• Confusing syntax errors with lifecycle behavior
• Assuming constructor is skipped

5. Given a list of objects created inside a function, when will their destructors be called?

class Item:
    def __init__(self, name):
        self.name = name
        print(f'Created {name}')
    def __del__(self):
        print(f'Deleted {self.name}')

def create_items():
    items = [Item('a'), Item('b'), Item('c')]
    print('Items created')

create_items()
print('Function ended')

hard

A. Destructors called immediately after 'Items created' inside the function

B. Destructors called before 'Items created'

C. Destructors never called because list holds references

D. Destructors called after 'Function ended' when function scope ends

Solution

1. Step 1: Analyze object references inside function

   Objects are stored in the list 'items' inside create_items(). They exist until the function ends.

2. Step 2: Determine when objects lose references

   When create_items() finishes, 'items' list is destroyed, removing references to objects, triggering destructors.

3. Step 3: Confirm output order

   So, 'Items created' prints, then function ends, then destructors print, then 'Function ended' prints.

4. Final Answer:

   Destructors called after 'Function ended' when function scope ends -> Option D

5. Quick Check:

   Objects destroyed after function scope ends [OK]

Hint: Objects destroyed when last reference goes out of scope [OK]

Common Mistakes:

• Thinking destructors run immediately after creation
• Assuming list keeps objects alive forever
• Confusing print order with destructor timing