None — Intermediate Playground

Represents the absence of a value; Python's null equivalent

Python Playground

def append_to(item, target=None):
    if target is None:
        target = []  # fresh list each call
    target.append(item)
    return target

a = append_to(1)
b = append_to(2)
print(a)
print(b)
print(a is b)

Output

Click "Run" to execute your code

Never use a mutable default argument like def f(x=[]). Use None as a sentinel and create the mutable object inside the function.

Challenge

Try modifying the code above to explore different behaviors. Can you extend the example to handle a new use case?

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