See also https://github.com/jailctf/pyjailbreaker
See also https://blog.pepsipu.com/posts/albatross-redpwnctf
It does still require letters to be able to spell attribute/function names (unless I'm reading it wrong in that blog post).
See also https://github.com/jailctf/pyjailbreaker
See also https://blog.pepsipu.com/posts/albatross-redpwnctf