3.2 Lesson Period 4 - None Data Abstraction

None - 3.2.9

None in Python

The None keyword is used to define a null value, or no value at all. None is not the same as 0, False, or an empty string. None is a data type of its own (NoneType) and only None can be None.

Purpose

• Represents the absence of a value or a null value in Python.
• Used to indicate that a variable has no data assigned to it.
• Can serve as a placeholder in data structures (like lists or dictionaries) to signify empty entries.
• Useful in conditional statements to check if a variable has been initialized or assigned a meaningful value.
• Helps distinguish between “no value” and other falsy values (like 0, False, or an empty string).

# Assigning None to a variable
result = None

# Checking if a variable is None
if result is None:
    print("The result has no value.")
else:
    print("The result has a value:", result)

# None is commonly used as a default argument in functions
def my_function(value=None):
    if value is None:
        print("No value provided.")
    else:
        print("Value provided:", value)

The result has no value.

Javascript Version

// Assigning null to a variable
let result = null;

// Checking if a variable is null
if (result === null) {
    console.log("The result has no value.");
} else {
    console.log("The result has a value:", result);
}

// null is often used as a default value in function arguments
function myFunction(value = null) {
    if (value === null) {
        console.log("No value provided.");
    } else {
        console.log("Value provided:", value);
}
}

// Calling the function with and without a value
myFunction();        // No value provided.
myFunction(42);      // Value provided: 42