I once wrote a custom build systems in python to generate Make files. I did this because I wanted to use convention instead of configuration and achieve fast builds on multicore machines. Later, after leaving that company, I wanted to recreate a similar build system. I wrote it in python to generate Ninja build files. I found it easier and cleaner to write Ninja build files.

I wasn't able to do a direct comparison of the build speeds of the two systems, but I bet the Ninja builds were significantly faster.