避免除以零

Question

我知道这是基本的，所以任何帮助表示赞赏。

这是我的代码 - 我只是无法使用 if 语句来避免除以零的工作。

谁能帮忙？

# problem: calculate what percent of car park spaces are occupied
# input: integers 1 or 0, 1 signals an occupied space and 0 is empty

car_park_spaces = []
          
# sub problem: number of occupied spaces
occupied = 0

for car_park_space in car_park_spaces:
    if car_park_space == 1:
        occupied += 1
    occupied_spaces = occupied

    # sub problem: find the length of the list
    percentage = occupied_spaces / len(car_park_spaces) * 100

    # output: percent of occupied spaces
    if not car_park_spaces:
        print('The list is empty')
    else:
        print ('The percentage of occupied spaces is', percentage, '%')

Answer 1

我将代码移到了函数中，这样它就更有条理了。函数如下所示：

def occupied_percent(car_park_spaces):
    if not car_park_spaces:
        return None
        
    occupied = 0
    total_spaces = len(car_park_spaces)

    for space in car_park_spaces:
        if space:
            occupied += 1

    return occupied / total_spaces * 100

如果百分比计算成功，则输出为float，否则输出为None。使用该函数时，您必须在打印结果之前检查返回值。

接下来我创建了简化使用的打印功能：

def print_percentage(car_park_spaces):
    result = occupied_percent(car_park_spaces)
    print('The list is empty.' if result is None else f'The percentage of occupied spaces is {result}%.')

我运行了一些测试用例：

print_percentage([])
print_percentage([0])
print_percentage([1])
print_percentage([1, 0])
print_percentage([1, 0, 1, 1])

那些产生这个输出：

The list is empty.
The percentage of occupied spaces is 0.0%.
The percentage of occupied spaces is 100.0%.
The percentage of occupied spaces is 50.0%.
The percentage of occupied spaces is 75.0%.

请注意，代码可能会进一步简化，因为 Python 倾向于使用大量单行代码。