import itertools
test = [[-1, -2], [30, 40], [25, 35]]
print(list(itertools.chain.from_iterable(test)))

#-> [-1, -2, 30, 40, 25, 35]

如果输入列表中有嵌入的列表或元组作为元素，那么就使用下面这种方法，不过也有个局限，它使用了 for 循环：

def unifylist(l_input, l_target):
    for it in l_input:
        if isinstance(it, list):
            unifylist(it, l_target)
        elif isinstance(it, tuple):
            unifylist(list(it), l_target)
        else:
            l_target.append(it)
    return l_target

test =  [[-1, -2], [1,2,3, [4,(5,[6,7])]], (30, 40), [25, 35]]

print(unifylist(test,[]))

#Output => [-1, -2, 1, 2, 3, 4, 5, 6, 7, 30, 40, 25, 35]