Truthiness & Boolean Logic

Python tests truthiness: every value is True or False in a condition. The falsy gang: 0, 0.0, "", [], {}, None, False. Everything else is truthy.

name = ""
if not name:
    print("name is empty — why not falsy check instead of len?")

Truthiness makes conditions read like English — but be explicit when 0 is a meaningful value rather than "missing".

Boolean logic

age = 20
has_ticket = True

if age >= 18 and has_ticket:
    print("enter")

| Expression | True when | | --- | --- | | a and b | both truthy | | a or b | at least one truthy | | not a | a is falsy |

Chained comparisons

A Python treat: 18 <= age < 65 does what it says. Use it — it matches how humans write ranges.