Are there any difficulties in generating a program in standard languages in Python? Did you choose a DSL because neural network is sensitive to the output programming language?
It turns out the full grammar of Python (and almost all real programming languages) is quite large; this is very early and new work in neural program synthesis, and so we chose a pretty limited DSL to make sure that we could at least solve this one before moving on to more general ones that contain state, conditionals, for-loops, etc. In theory however, we can apply the exact architecture to Python programs and see what happens. We haven't tried yet. :)