当值可以为“`None`”时，将两个字典的值相除。

if dict[key] is None:
    # 处理值为None的情况

def divide_values(dict1, dict2, key):
    if key not in dict1 or key not in dict2:
        print("键不存在于字典中")
        return None
    
    if dict1[key] is None or dict2[key] is None:
        print("值为None")
        return None
    
    try:
        result = dict1[key] / dict2[key]
        return result
    except ZeroDivisionError:
        print("除数为0")
        return None

# 示例字典
dict1 = {'a': 10, 'b': 20, 'c': None}
dict2 = {'a': 5, 'b': 0, 'c': 30}

# 调用函数进行除法运算
result = divide_values(dict1, dict2, 'b')
if result is not None:
    print("除法结果:", result)