Python was always slow to start. Not as slow as the JVM, but maybe around the 300th test case for hg and maybe around the 100th python script invocation in any build system, people should start to wonder about how to get all of that under one Python process.
It's not like Python is so ugly it'd be messy to do. (It was possible with the JVM after all. It even works by simply forking the JVM, with all its GC threads and so on: https://github.com/spray/sbt-revolver )
Make style DAGs are nice, but eventually the sheer number of syscalls for process setup (and module import and dynamic linking) are going to be a waste of time.
It's not like Python is so ugly it'd be messy to do. (It was possible with the JVM after all. It even works by simply forking the JVM, with all its GC threads and so on: https://github.com/spray/sbt-revolver )
Make style DAGs are nice, but eventually the sheer number of syscalls for process setup (and module import and dynamic linking) are going to be a waste of time.