← Back

Home › Output practice › truthiness and the ternary

Predict the output: truthiness and the ternary

🔮 Predict the outputTopic: operatorsDifficulty: mediumNo login needed

The snippet

if x: does not ask whether x is a boolean; it asks whether x is *truthy*. Once you know the small list of false values, every other object — including the string "0" — is true.

count = 0
label = "ready" if count else "empty"
print(label, bool("0"), bool([]))

Your prediction

Type exactly what this program prints — one line per print() call:

The output

empty True False

Verified against CPython 3.11 in this repo's build

Line-by-line explanation

  1. count = 0
    Zero is one of Python's few falsy values, so count is false in a condition.
  2. label = "ready" if count else "empty"
    The condition is false → the else branch → "empty". Read the conditional expression in English order: *ready if count, else empty*.
  3. bool("0")
    True — a non-empty string is truthy no matter what it contains, including "0", " " and "False".
  4. bool([])
    False — empty containers are falsy (list, tuple, dict, set, str).
  5. printed together
    empty True False.

The rule you can reuse

Falsy: False, None, numeric zero of every type, and every empty sequence/collection. Everything else is truthy. Write if not items: rather than if len(items) == 0:.

Why most predictions break here

Calling bool("0") False because it prints as zero. Only the *number* 0 is falsy — text of length 1 is not. And if count == False is a different question from if count.

Quick fire

Same rule, two more shapes. Predict first, then open.

Predict this too
print("yes" if [] else "no")
print(1 < 2 < 3, 3 > 2 > 1)

Output
no
True True

An empty list is falsy → no; comparison chaining means 1 < 2 and 2 < 3 → True True.

Predict this too
print(not 0 and "ok")
print("" or "fallback")
print(5 and None)

Output
ok
fallback
None

and/or return an object, not a bool: ok, fallback, None.

Share your result

Challenge a friend — the link contains the question, never the answer:

Copied ✓

Keep practising this rule

More output questions → All interactive problems

Questions this page answers

Why do and/or return objects instead of True/False?

They short-circuit and hand back the value that decided the result — which is what makes name = input() or "anonymous" work. Wrap in bool() when you need a real boolean.

Is 1 == True a trap too?

It is True, because bool is a subclass of int and 1 equals True. Use x is True only when you genuinely mean "that exact object", never for numbers.