Logical Operators¶

Operator	Description	C# Mapping
`and`	Logical AND (short-circuit)	`&&`
`or`	Logical OR (short-circuit)	`\\|\\|`
`not`	Logical NOT	`!`

Truthiness¶

Operands of and, or, and not are evaluated for truthiness — the same rule that governs if, while, assert, ternary conditions, comprehension filters, and match guards. A type is truth-testable when it has a falsy case:

Type	Truthiness lowering	Falsy value
`bool`	identity	`False`
`int`	`x != 0`	`0`
`float`	`x != 0.0`	`0.0`
`long`	`x != 0L`	`0L`
`str`	`x.Length > 0`	`""`
`bytes`	`((ISized)x).Count > 0`	`b""`
collections (`list`, `dict`, `set`, `tuple`)	`((ISized)x).Count > 0`	empty
`None`	`false` (always)	`None`
`Optional[T]`	`x.IsSome`	`None()`
`T?` (nullable)	`x != null`	`None`
UDT with `__bool__`	`x.IsTrue`	implementation-defined
UDT with `__len__`	`((ISized)x).Count > 0`	empty
objects, functions, delegates	refused (SPY0220)	no falsy case

Deviation from Python: Python makes objects without __bool__/__len__ vacuously truthy. Sharpy refuses them — the check can never do anything useful.

Return Type¶

and and or return bool, not the operand value. This is a deliberate deviation from Python, where "" or "Anonymous" returns "Anonymous". In Sharpy, "" or "Anonymous" evaluates to True. See null_coalescing_operator.md for the ?? operator that provides the Python-style fallback behavior.

Examples¶

x: int = 42
if x and x > 0:
    print("positive")

name: str = ""
result: bool = name or "fallback"  # True (both sides truth-tested)

xs: list[int] = [1, 2, 3]
print(not xs)  # False (non-empty list is truthy)