This was posted previously at https://news.ycombinator.com/item?id=4923530, along with some fairly extensive discussion and criticism.

The basic gist of the criticism seems to be the code is basically just directly translating a Python token list (not an AST) into Javascript, and as such is reasonably fragile and horrible code (the main translator function: https://code.google.com/p/brython/source/browse/trunk/py2js.... ).