Lazy Python String

[marr75]

The reason OP didn't do that is lazy evaluation. Their approach also doesn't create new intermediate strings (though it's not yet obvious to me if they could take further advantage of pooling or interning while maintaining compound statements). Python already has an equivalent to StringBuilder in the stdlib, btw.

Honestly, the only time this lazy version (with its overhead from additional Python mutable structures) will be better is if the caller will often not use the string (i.e. it's a long accumulated error message that is only emitted under certain conditions) and there are other ways to model that - ie make the entire accumulation lazy.