True — Advanced Examples

Boolean literal representing true/1

EasyIntermediateAdvancedExpert

Custom truthy objects

Controlling truthiness via __bool__ and __len__.

python
class QueryResult:
    def __init__(self, rows):
        self.rows = rows

    def __bool__(self):
        return len(self.rows) > 0

    def __len__(self):
        return len(self.rows)

empty = QueryResult([])
full = QueryResult([{"id": 1}, {"id": 2}])

print(f"Empty result: {bool(empty)}")
print(f"Full result: {bool(full)}")
if full:
    print(f"Got {len(full)} rows")

Python calls __bool__ first; if not defined, falls back to __len__. If neither exists, the object is always truthy.

Want to try these examples interactively?

Open Advanced Playground
← Intermediate ExamplesExpert Examples →