Easy

Have a go at it. The editor and the docs panel are open, and your code is saved as you type. Running it needs a free account — you’ll come back to exactly what you wrote.

Comparing Values: == and is

~9 mincode completion

Two different questions, two different operators:

  • == asks is this the same value?
  • is asks is this the same object in memory?

    • Almost always you want ==.

    a = [1, 2]
b = [1, 2]

a == b      # True     same contents
a is b      # False    two separate lists that happen to match

    is has exactly one common correct use: comparing against None.

    if value is None:       # correct, and what everyone writes
if value == None:       # works, but not idiomatic

    There is a related trap. if not value: is not the same as if value is None:, because 0, "" and [] are all falsy but are not None:

    value = 0
if not value:           # True!   even though a value was supplied
if value is None:       # False   which is what you meant

    That distinction matters the moment a real value can legitimately be zero, which in data work is constantly.

    Your task:

    Write describe(value) that returns:

  • "missing" when the value is None
  • "empty" when it is an empty list
  • "present" for anything else, including 0 and an empty string

    • Example Tests

    None is missing

    Input: {"value":null}

    Expected: "missing"

    An empty list is empty

    Input: {"value":[]}

    Expected: "empty"

    Zero is a real value, so it is present, not missing

    Input: {"value":0}

    Expected: "present"

    Python
    def describe(value):
    """
    Classify a value as missing, empty, or present.

    Args:
        value: anything, possibly None

    Returns:
        "missing" for None, "empty" for [], "present" otherwise.
    """
    # YOUR CODE HERE
    pass

    Run your code to see results

    ⌘↵ runs against the visible tests

    Loading docs…