Learn Identity vs Equality | Booleans and Comparisons

Learn the difference between identity and equality in Python. Identity checks whether two variables refer to the same object in memory, while equality compares whether two objects hold the same value. Grasping this distinction is key to writing accurate conditionals, validations, and data-processing logic.

What is `is`?

is checks object identity, whether two variables point to the same object in memory;
== checks equality of values, whether two objects have the same contents.


              12345678
            
# Comparing two shopping carts in an online store
cart_today = ["milk", "bread"]
cart_yesterday = ["milk", "bread"]
shared_cart = cart_today

print(cart_today == cart_yesterday)  # True → same items
print(cart_today is cart_yesterday)  # False → two separate cart objects
print(cart_today is shared_cart)     # True → both refer to the same cart

When to Use `is` and When to Avoid It

Use is in comparison with singletons such as None;


              12345
            
# Checking if the user has entered their phone number
user_phone = None

if user_phone is None:
    print("No phone number provided yet")

is not is the negated identity check;


              12345
            
# Checking if the user's age is stored in the system
user_age = 64

if user_age is not None:
    print(f"User age is recorded: {user_age}")

Avoid using is to check for equality between numbers or strings. Due to internal caching/interning, identity may appear to "work" sometimes, but it's not reliable across different runs and environments, use == instead;


              123456789101112
            
# Comparing user IDs and usernames in a system
user_id_a = 256
user_id_b = 256

print(user_id_a == user_id_b)  # True → same user ID value
print(user_id_a is user_id_b)  # May appear True, but identity check is unreliable for numbers

username_a = "hello"
username_b = "he" + "llo"

print(username_a == username_b)  # True → same text
print(username_a is username_b)  # Avoid using 'is' for string comparison (implementation detail)

For booleans, prefer truthiness checks.


              12345
            
# Checking if dark mode is enabled in user settings
dark_mode_enabled = True

if dark_mode_enabled:  # clearer than: if dark_mode_enabled is True
    print("Dark mode is ON")

1. Fill in the blanks with `is` or `==`:

2. What's the correct way to test for "no value"?

3. Which statement is recommended?

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Thanks for your feedback!

Section 2. Chapter 3

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What is `is`?

is checks object identity, whether two variables point to the same object in memory;
== checks equality of values, whether two objects have the same contents.


              12345678
            
# Comparing two shopping carts in an online store
cart_today = ["milk", "bread"]
cart_yesterday = ["milk", "bread"]
shared_cart = cart_today

print(cart_today == cart_yesterday)  # True → same items
print(cart_today is cart_yesterday)  # False → two separate cart objects
print(cart_today is shared_cart)     # True → both refer to the same cart

When to Use `is` and When to Avoid It

Use is in comparison with singletons such as None;


              12345
            
# Checking if the user has entered their phone number
user_phone = None

if user_phone is None:
    print("No phone number provided yet")

is not is the negated identity check;


              12345
            
# Checking if the user's age is stored in the system
user_age = 64

if user_age is not None:
    print(f"User age is recorded: {user_age}")

Avoid using is to check for equality between numbers or strings. Due to internal caching/interning, identity may appear to "work" sometimes, but it's not reliable across different runs and environments, use == instead;


              123456789101112
            
# Comparing user IDs and usernames in a system
user_id_a = 256
user_id_b = 256

print(user_id_a == user_id_b)  # True → same user ID value
print(user_id_a is user_id_b)  # May appear True, but identity check is unreliable for numbers

username_a = "hello"
username_b = "he" + "llo"

print(username_a == username_b)  # True → same text
print(username_a is username_b)  # Avoid using 'is' for string comparison (implementation detail)

For booleans, prefer truthiness checks.


              12345
            
# Checking if dark mode is enabled in user settings
dark_mode_enabled = True

if dark_mode_enabled:  # clearer than: if dark_mode_enabled is True
    print("Dark mode is ON")

1. Fill in the blanks with `is` or `==`:

2. What's the correct way to test for "no value"?

3. Which statement is recommended?

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 3

Identity vs Equality

What is is?

When to Use is and When to Avoid It

1. Fill in the blanks with is or ==:

2. What's the correct way to test for "no value"?

3. Which statement is recommended?

Awesome!

Identity vs Equality

What is is?

When to Use is and When to Avoid It

1. Fill in the blanks with is or ==:

2. What's the correct way to test for "no value"?

3. Which statement is recommended?

What is `is`?

When to Use `is` and When to Avoid It

1. Fill in the blanks with `is` or `==`:

What is `is`?

When to Use `is` and When to Avoid It

1. Fill in the blanks with `is` or `==`: