Python nicest way to take boolean expression string apart

Question

I have a boolean expression string, that I would like to take apart:

condition = "a and (b or (c and d))"

Or let's say:
I want to be able to access the string contents between two parenthesis.
I want following outcome:

"(b or (c and d))"
"(c and d)"

I've tried the following with regular expressions (not really working)

x = re.match(".*(\(.*\))", condition)
print x.group(1)

Question:
What is the nicest way to take a boolean expression string apart?

Answer 1

This is the sort of thing you can't do with a simple regex. You need to actually parse the text. pyparsing is apparently excellent for doing that.

Answer 2

Like everyone said, you need a parser.

If you don't want to install one, you can start from this simple top-down parser (take the last code sample here)

Remove everything not related to your need (+, -, *, /, is, lambda, if, else, ...). Just keep parenthesis, and, or. You will get a binary tree structure generated from your expression. The tokenizer use the build-in tokenize (import tokenize), which is a lexical scanner for Python source code but works just fine for simple cases like yours.