Qgis Function grabbing a value from a list

values_from_list.py

from qgis.core import *
from qgis.gui import *

@qgsfunction(args='auto', group='Custom')
def values_from_list(string, number, feature, parent):
	"""
	Takes the n-th value from a list in a field where the list is 
	written like: (3:value1, value2,value3). Such lists are often a
	result of importing gml. <br />
	
	<h3>Syntax</h3>
	
	values_from_list(<i>string</i>, <i>number</i>)
	
	<h3>Arguments</h3><br/>
	
	<i>string</i> The string containing the list in format like (3:value1, value2,value3) <br/>
	<i>number</i> The index number of the value in the list to return
	
	<h3>Examples</h3>
	
	<pre>values_from_list("text", 1)</pre>
	
	"""
	
	components = string.strip('()').split(':',1)
	values_list = components[1]
	try:
		return values_list.split(',')[number - 1]
	except:
		return None

When using a function like this for openbareruimtelabel from the BGT, then the following regex based expression grabs the last value as it should to use the right rotation for a label:

to_real(regexp_substr(  "hoek"  , '([-]?\\d+(\\.\\d+)?)[)]'))