NoShortCircuit

Misconception:

Expressions with operators and and or always evaluate both of their operands.

and/or always evaluate both operands

and/or evaluate their right operand only if absolutely necessary

These two operators are short-circuit operators, which means they first evaluate the left operand and then only evaluate the right operand if that’s absolutely necessary.

Use in a common idiom

This misconception provides an opportunity to discuss the following idiom, which would cause an AttributeError ('NoneType' object has no attribute 'value') if it always evaluated its right-hand operand, even when Node is None:

if node is not None and node.value < v:
    ...

Short circuiting also applies to chained comparisons. For example, if we have a comparison x < y <= z and x < y is False then z is not evaluated.

Python

plr3.8

Library Boolean operations

Expression Evaluation Operator Boolean Control Flow

expression involving short-circuit operator

graph of conditional involving short-circuit operator

Java

NoShortCircuit