Question

I have a genetic program that prints the expression tree to a file (it can easily switch between pre/post/in-fix)

It seems like pre-fix would be the easiest to parse so I am currently using that.

How would I go about parsing this string using python 2.7? For example, how would I parse the string +(*(2,1),*(4,3)) ~~~~ which is 2*1+4*3

f = open('expression_tree.txt', 'r')
input = f.read()
root_node_operator = input[0]

That’s about as far as I’ve gotten. I’m not that familiar with parsing. Thanks!

I have one python program that prints the expression tree data structure and I want to parse it and evaluate it in the next python program.

Or is there a way to pass the expression tree object to the next python program so no parsing is needed? like I have my tree called test_tree in GP.py. Can I somehow get at that from my other file MyBot.py?

Answer 1

replace +(*(2,1),*(4,3)) with (+ (* 2 1) (* 4 3)), then pipe to scheme

$ echo '+(*(2,1),*(4,3))' | sed 's/\(.\)(/(\1 /g; s/,/ /g' | scheme | sed -n '/;Value: /s///p'

If you want to use python, please try pyparsing.