It's pretty horrible, but this adds support for parentheses inside the `full_eval` function:

  from itertools import takewhile, dropwhile

  def split_paren(expr):
      left = ''.join(takewhile(lambda c: c != '(', expr))
      right = ''.join(takewhile(lambda c: c != ')', expr[::-1]))[::-1]
      inside = ''.join(dropwhile(lambda c: c != ')', ''.join(dropwhile(lambda c: c != '(', expr))[::-1]))[::-1][1:-1]
      return left, inside, right

  def full_eval(expr):
      if '(' in expr:
          left, inside, right = split_paren(expr)
          return full_eval(left + str(full_eval(inside)) + right)
      else:
          return calc(expr)

Neat! Well, sort of. Sometimes, certain things would look nicer not written in Python...

This is pretty clever. There's a video by Jonathan Blow, creator of Braid and currently making a programming language called Jai, that talks about parsing expressions with order of operations. He gives an simple approach that apparently was discovered recently (though he didn't remember the paper name) that does this in a single pass and hardly any more complicated than what you wrote. You can see it here [1]. He also trashes on using yacc/bison before that and on most academic parsing theory.

[1] https://www.youtube.com/watch?v=MnctEW1oL-E&t=4578s

Reverse Polish notation (RPN) > Converting from infix notation https://en.wikipedia.org/wiki/Reverse_Polish_notation#Conver... > Shunting-yard algorithm https://en.wikipedia.org/wiki/Shunting-yard_algorithm

Infix notation supports parentheses.

Infix notation: 3 + 4 × (2 − 1)

RPN: 3 4 2 1 − × +

I would like to know the name of that paper if anyone knows.

I believe he was talking about Pratt parsing in the video.

Top Down Operator Precedence - Vaughan R. Pratt - https://tdop.github.io/

What he called "priority" is called "binding power" in the paper.

I like Jonathan Blow and all, but he should be careful with trashing academic parsing theory if he thinks that Pratt parsing was only discovered "in the last few years".

It sounds a lot like Pratt parsing, or at least the way I usually implement it. But I don't what paper he is referring to.

I think you have expanded my python horizons, thank you!