freeCodeCamp/guide/english/python/truth-value-testing/index.md

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Python Truth Value Testing

Python Docs - Truth Value Testing

Any object can be tested for truth value, for use in an if or while condition or as operand of a Boolean operation like and, or, or not.

The following values are considered false:

• None
• False
• zero of any numeric type, for example, 0, 0.0, 0j, Decimal(0), Fraction(0, 1).
• any empty sequence, for example, '', (), [], set(), range(0).
• any empty mapping, for example, {}.
• instances of user-defined classes, if the class defines a __bool__() or __len__() method, when that method returns False or 0.

All other values are considered true -- so objects of many types are always true.

Operations and built-in functions that have a Boolean result always return 0 or False for false and 1 or True for true, unless otherwise stated. (Important exception: the Boolean operations or and and always return one of their operands.)