task = self.config[taskName]

        sourceText = [(os.path.splitext(os.path.basename(file))[0],
                open(file, 'r', encoding=task['Source encoding']).read())
                for file in glob.glob(task['Source files'])]

        # Возможно, нужно улучшить...
        separator = task['Split'] if 'Split' in task.keys() else None
        if separator:
            s = []
            for file, text in sourceText:
                s.extend([(file, t) for t in text.split(separator)])
            sourceText = s
        # ----------

arr = [(1, 'a,b'), (2, 'c,d,e')] 
res = []
for ix, s in arr:
 for char in s.split(","):
  res.append((ix, char))
print(res)

>>> l = [(1, 'a,b'), (2, 'c,d,e')]
>>> [(a, i) for a, b in l for i in b.split(',')]
[(1, 'a'), (1, 'b'), (2, 'c'), (2, 'd'), (2, 'e')]

        separator = task['Split'] if 'Split' in task.keys() else None
        if separator: sourceText = \
            [(a, c) for a, b in sourceText for c in b.split(separator)]