Change length inside a list when connector is unconnected in python

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@Nick_Boyts , I have almost the solution, I have changed the values inside the loop but when I try to set them inside the parameter I got an error:
image

elements and values structure list:
image
What do I miss?

elementen = UnwrapElement(IN[0])

TransactionManager.Instance.EnsureInTransaction(doc)
#connectors controleren en unconnected pipes over houden
lengtes = []

for pipe in elementen:
	for p in pipe:
		lengtes.append([])
		for i in p:
			namen = GetName(i)
			try:
				conns = i.ConnectorManager.Connectors
			except:
				conns = i.MEPModel.ConnectorManager.Connectors
			for conn in conns:
				if conn.IsConnected and namen.Contains("Alupex"):
					lengte = i.get_Parameter(RDB.BuiltInParameter.CURVE_ELEM_LENGTH).AsValueString()
					lengtes[-1].append(int(lengte))
				elif namen.Contains("Alupex"):
					lengte = 1500
					lengtes[-1].append(int(lengte))						
				else:
					lengte = i.LookupParameter("Length").AsValueString()
					lengtes[-1].append(int(lengte))
			section_lengte = []	
			for l in lengtes:
				s = 0
				section_lengte.append([[sum(l)]])
				i.LookupParameter("Section lengte").Set(section_lengte[s])
				s +=1

#einde transactie
TransactionManager.Instance.TransactionTaskDone()

OUT =  section_lengte