Question

Problem

There is a program file that contains the following code snippet at some point in the file.

...

food($apples$ , $oranges$ , $pears$ , $tomato$){
  ...
}

...

This function may contain any number of parameters but they must be strings separated by commas. All the parameter strings are lowercase words.

I want to be able to parse out each of the parameters using a regular expression. For example the resulting list in python would be as follows:

["apples", "oranges", "pears", "tomato"]

Attempted Solution

Using the python RE module, I was able to achieve this by breaking the problem into two parts.

1. Find the function in the code and extract the list of parameters.

   plist = re.search(r'food\((.*)\)', programString).group(1)
   

2. Split the list using another regular expression.

   params = re.findall(r'[a-z]+', plist)
   

Question

Is there anyway I could achieve this with one regular expression instead of two?

Edit

Thanks to Tim Pietzcker’s answer I was able to find some related questions:

1. Python regular expressions – how to capture multiple groups from a wildcard expression?
2. Which regex flavors support captures (as opposed to capturing groups)?

Answer 1

To answer your question “Can it be done in a single regex?”: Yes, but not in Python.

If you want to match and capture (individually) an unknown number of matches as in your example, using only a single regular expression, then you need a regex engine that supports captures (as opposed to capturing groups). Only .NET and Perl 6 do this currently.

So in Python, you either need to do it in two steps (find the entire food(...) function call, and then findall individual matches with a second regex as suggested by Dingo).

Or use a parser like Paul McGuire’s pyparsing.