simpler, safer, and more general. Unlike when passing objects by pointer or reference, there’s no risk of confusion over ownership, lifetime, mutability, and similar issues, and no need to specify them {} // Bad, defines only move constructor, but not operator=. private: Field field_; }; Due to the risk of slicing, avoid providing an assignment operator or public copy/move constructor for a class that’s semantics of the built-in operators. • Operators are often defined outside the class, so there’s a risk of different files introducing different definitions of the same operator. If both defini- tions are

preferable to if len(seq): or if not len(seq):. • When handling integers, implicit false may involve more risk than benefit (i.e., accidentally handling None as 0). You may compare a value which is known to be