short code review: - the `tokens` method returning a variable-length tuple is a very bad idea; modern Python supports the `datatype` decorator which should be

short code review: - the `tokens` method returning a variable-length tuple is a very bad idea; modern Python supports the `datatype` decorator which should be used in this case - I'd strongly recommend using a regex for lexing; much easier to get it right than a long if/elif/else block - I'd recommend refactoring code and implementing the `next_token` logic so that it works for any generator; an example implementation could be (WARNING: I wrote this in 5min, would require extensive unittests!) class Peek: def __init__(self, it): self.cur, self.nxt = itertools.tee(it, 2) self.current = next(self.cur) def __next__(self): self.current = next(self.cur) return next(self.nxt) - statements with a "prefix" (like `print X` or `if Y`) are very easy to parse (just use the lookahead token!) but when you get to parsing expressions, I strongly recommend using a Pratt parser (extensible operator precedence parsing)