On Posix systems (e.g. GNU/Linux) Python includes the ability to fork (”A fork, when applied to computing occurs when a process creates a copy of itself, which then acts as a ‘child’ of the original process, now called the ‘parent’.” - Wikipedia).
By default the debugger will pause (break) the debuggee when it identifies that a fork is about to be attempted. At that point you may choose if you would like the debugger to continue debugging the parent or the child process.
To debug the child process type ‘fork child‘ at the console, and then request the debugger to continue.
The console ‘fork‘ command accepts the following arguments: child, parent, auto, manual. With no arguments the console ‘fork’ command returns the current state. Type ‘help fork‘ at the console for more information.
On some Posix OS such as FreeBSD, Stepping into the child fork can result in termination of the child process since the debugger uses threading for its operation and on these systems threading and forking can conflict.