Comment by kerneloops

A survey of some other languages:

C printf: MT-Safe locale.

C++ std::cout: safe, unless you call sync_with_stdio(false).

JVM System.out.println: safe in common JVMs.

C# Console.WriteLine: safe.

Go fmt.Printf: safe.

Rust println!: safe.

Ruby puts: safe.

So it seems that Python is the outlier here.