Question

我的代码是打印列表中元组的平均值，如果列表为空则返回None。现在这是我的代码

def average_vehicles(vehicle_records):
    """Return average of vehicles"""
    summ = 0
    num = 0
    average = 0
    if vehicle_records != []:
        for value in vehicle_records:            
            summ += value[1]
            num += 1
        average = summ / num
    else:
        average  = "None" 
    return average

我得到了此测试代码的正确输出：

some_records = [('2010-01-01',100),
            ('2010-01-02',200),
            ('2010-01-03',300)]
avg = average_vehicles(some_records)
print(avg)

但是我无法打印出来＃34;好的＆＃34;对于以下测试代码而且我不确定为什么当其他一切看起来不正常时，有人可以帮忙吗？

some_records = []
avg = average_vehicles(some_records)
if avg is None:
   print('OK')
else:
   print('The function should return a None value')

Answer 1

您将返回字符串"None"而不是对象None

Answer 2

None和"None"不是一回事。

Answer 3

None不应该是字符串而是None对象。将以下行average = "None"更改为average = None，它应该有效。

Answer 4

some_records = []
avg = average_vehicles(some_records)
if avg == "None":
   print('OK')
else:
   print('The function should return a None value')

Answer 5

some_records = []
avg = average_vehicles(some_records)
if avg == 'None':
   print('OK')
else:
   print('The function should return a None value')

说明：

当我们打印avg的类型时，它的类型为str，但如果我们选中avg is None，则此None的类型为Nonetype。所以我们需要检查使用＆＃34;无＆＃34;作为avg == 'None'

如何打印列表中元组平均值的消息

5 个答案: