从数字列表返回3个最大值的函数出错

问题描述

我有这个数据文件，我必须找到它包含的3个最大数字

24.7    25.7    30.6    47.5    62.9    68.5    73.7    67.9    61.1    48.5    39.6    20.0
16.1    19.1    24.2    45.4    61.3    66.5    72.1    68.4    60.2    50.9    37.4    31.1
10.4    21.6    37.4    44.7    53.2    68.0    73.7    68.2    60.7    50.2    37.2    24.6
21.5    14.7    35.0    48.3    54.0    68.2    69.6    65.7    60.8    49.1    33.2    26.0
19.1    20.6    40.2    50.0    55.3    67.7    70.7    70.3    60.6    50.7    35.8    20.7
14.0    24.1    29.4    46.6    58.6    62.2    72.1    71.7    61.9    47.6    34.2    20.4
8.4     19.0    31.4    48.7    61.6    68.1    72.2    70.6    62.5    52.7    36.7    23.8
11.2    20.0    29.6    47.7    55.8    73.2    68.0    67.1    64.9    57.1    37.6    27.7
13.4    17.2    30.8    43.7    62.3    66.4    70.2    71.6    62.1    46.0    32.7    17.3
22.5    25.7    42.3    45.2    55.5    68.9    72.3    72.3    62.5    55.6    38.0    20.4
17.6    20.5    34.2    49.2    54.8    63.8    74.0    67.1    57.7    50.8    36.8    25.5
20.4    19.6    24.6    41.3    61.8    68.5    72.0    71.1    57.3    52.5    40.6    26.2

因此，我编写了以下代码，但它只搜索第一行数字，而不是整个列表。是否有人可以帮助查找错误？

def three_highest_temps(f):
    file = open(f, "r")
    largest = 0
    second_largest = 0
    third_largest = 0
    temp = []
    for line in file:
        temps = line.split()

        for i in temps:
            if i > largest:
                largest = i
            elif largest > i > second_largest:
                second_largest = i
            elif second_largest > i > third_largest:
                third_largest = i
        return largest, second_largest, third_largest

print(three_highest_temps("data5.txt"))

推荐答案

您的return语句在for循环中。一旦到达RETURN，函数就会终止，因此循环永远不会进入第二次迭代。通过减少缩进将return移出循环。

    for line in file:
        temps = line.split()

        for i in temps:
            if i > largest:
                largest = i
            elif largest > i > second_largest:
                second_largest = i
            elif second_largest > i > third_largest:
                third_largest = i
    return largest, second_largest, third_largest

此外，您的比较不会起作用，因为line.split()返回字符串列表，而不是浮点数。(如前所述，您的数据由浮点数组成，而不是整数。我假设任务是找到最大的浮存。)因此，让我们使用float()

您的代码仍然不会正确，因为当您找到一个新的最大值时，您将完全丢弃旧的值。相反，您现在应该将其视为第二大已知值。同样的规则适用于第二到第三大。

    for line in file:
        temps = line.split()

        for temp_string in temps:
            i = float(temp_string)
            if i > largest:
                third_largest = second_largest
                second_largest = largest
                largest = i
            elif largest > i > second_largest:
                third_largest = second_largest
                second_largest = i
            elif second_largest > i > third_largest:
                third_largest = i
    return largest, second_largest, third_largest

现在还有最后一个问题：

您忽略了I与最大值之一相同的情况。在这种情况下，i > largest将是假的，但largest > i也是假的。您可以将这两个比较中的任何一个更改为>=来修复此问题。

    for line in file:
        temps = line.split()

        for temp_string in temps:
            i = float(temp_string)
            if i > largest:
                third_largest = second_largest
                second_largest = largest
                largest = i
            elif i > second_largest:
                third_largest = second_largest
                second_largest = i
            elif i > third_largest:
                third_largest = i
    return largest, second_largest, third_largest

这样可以避免意外过滤掉i == largest和i == second_largest边缘案例。

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