'read data in sheet - to be used at writing time'

def _get_cache(self):

    cache = []
    if self.pos2:
        for row in range(self.pos1[0], (self.pos2[0] + 1)):
            for col in range(self.pos1[1], (self.pos2[1] + 1)):
                cache.append(self.sheet.cell(row=row, column=col).value)
    else:
        cell = self.sheet.cell(row=self.pos1[0], column=self.pos1[1])
        cache.append(cell.value)
    return cache
