计算平均值时如何从列表中排除0值

Question

我有一张这样的成绩清单：

/*
* 提示：该行代码过长，系统自动注释不进行高亮。一键复制会移除系统注释 
* grades = [[[4.0, 3.0], [3.0, 3.0], [4.0, 3.0], [3.33, 3.33], [3.0, 3.0], [4.0, 3.67], [3.0, 3.67], [4.0, 3.0], [4.0, 3.33], [4.0, 3.33], [3.0, 3.0], [3.67, 3.67], [3.33, 3.0], [4.0, 3.0], [3.0, 3.67], [3.33, 4.0], [4.0, 3.33], [4.0, 4.0], [3.0, 3.67], [3.0, 3.67], [3.67, 3.33], [4.0, 3.0], [3.0, 4.0], [3.67, 3.67], [4.0, 3.33], [2.33, 2.0], [3.0, 2.67], [2.67, 3.67], [2.33, 2.0]], [[3.0, 3.67], [3.33, 4.0]], [[2.33, 4.0]], [[4.0, 0], [3.67, 0], [3.67, 0], [4.0, 0], [3.0, 0], [3.67, 0], [3.33, 0], [3.0, 0], [3.67, 3.67], [3.0, 0], [4.0, 0], [4.0, 0], [3.0, 0], [3.67, 0], [3.0, 0], [4.0, 0], [3.0, 0], [3.33, 0], [4.0, 0], [4.0, 0], [3.33, 0], [0, 3.33], [3.33, 0], [4.0, 3.0], [4.0, 0], [4.0, 0]], [[3.0, 3.67], [3.67, 3.67], [4.0, 3.67], [3.0, 3.0], [3.0, 3.0], [3.67, 4.0], [4.0, 3.0], [3.33, 4.0], [3.67, 3.33], [3.0, 3.67], [3.67, 3.0], [3.0, 3.0], [3.0, 3.33], [3.33, 3.0], [4.0, 3.67], [3.33, 4.0], [4.0, 3.33], [3.67, 3.0], [3.67, 4.0], [3.0, 3.33], [3.0, 3.0], [3.67, 4.0], [3.67, 3.0], [3.33, 3.67], [3.0, 3.33], [3.33, 4.0], [3.0, 4.0], [3.0, 4.0], [3.33, 3.33], [3.33, 3.33], [3.67, 3.33], [4.0, 3.67], [3.33, 3.33], [4.0, 3.67], [3.33, 3.67], [4.0, 3.33], [3.67, 3.0], [3.33, 3.0], [3.67, 3.33], [3.0, 4.0], [3.67, 4.0], [3.67, 3.0], [3.67, 3.33], [3.33, 3.33], [3.67, 3.0], [4.0, 4.0], [3.0, 3.67], [3.0, 3.0], [3.0, 3.0], [3.33, 4.0], [3.67, 4.0], [3.0, 4.0], [3.67, 3.67], [3.0, 3.33], [3.67, 4.0], [3.33, 3.33], [4.0, 4.0], [3.33, 4.0], [3.33, 4.0], [3.0, 3.67], [4.0, 3.33], [3.33, 4.0], [3.0, 3.0], [3.33, 3.67], [3.33, 4.0], [3.67, 3.33], [3.67, 3.33], [4.0, 3.67], [3.67, 4.0], [3.67, 3.0], [3.33, 3.33], [3.0, 3.67], [3.67, 3.33], [3.33, 3.0], [3.33, 4.0], [3.0, 3.0], [3.33, 4.0], [3.33, 4.0], [4.0, 3.67], [4.0, 3.0], [3.67, 4.0], [3.33, 3.0], [3.67, 3.67], [3.67, 3.0], [3.33, 3.0], [4.0, 4.0], [3.33, 4.0], [3.0, 3.33], [3.67, 3.0], [4.0, 3.33], [3.67, 4.0], [3.0, 2.33], [2.0, 3.33], [2.0, 3.67], [2.0, 2.33], [3.67, 3.33], [2.0, 2.33], [3.67, 2.33], [2.33, 3.67], [3.67, 3.67], [3.33, 2.67], [3.33, 2.0], [3.67, 4.0], [2.0, 4.0], [4.0, 2.0], [3.0, 2.0], [2.33, 2.67], [4.0, 4.0], [3.0, 2.33], [3.0, 3.33], [2.33, 3.0], [4.0, 3.33], [3.67, 4.0], [2.0, 2.0], [2.33, 4.0], [4.0, 2.0], [2.67, 3.33], [2.0, 3.67], [3.33, 4.0]], [[3.0, 0], [3.33, 0], [3.67, 0], [3.67, 0], [3.67, 0], [3.33, 0], [3.0, 0], [3.0, 0], [3.33, 0], [3.0, 0], [4.0, 0], [3.0, 0], [3.0, 0], [3.67, 0], [3.67, 3.67], [3.67, 0], [3.67, 0], [4.0, 0], [3.67, 0], [3.0, 0], [3.0, 0], [4.0, 0], [3.0, 0], [3.0, 0], [3.0, 0], [3.33, 0], [3.0, 0], [3.67, 0], [4.0, 0], [3.0, 0], [3.0, 0], [3.0, 0], [3.33, 0], [4.0, 0], [4.0, 0], [3.67, 0], [4.0, 0], [3.33, 0], [3.0, 0], [3.67, 0], [3.67, 0], [4.0, 0], [3.33, 0], [3.33, 0], [4.0, 0], [3.33, 0], [3.33, 0], [3.0, 0], [3.0, 0], [3.67, 0], [4.0, 0], [0, 3.0], [3.33, 0], [4.0, 0], [3.67, 0], [4.0, 0], [0, 4.0], [0, 3.33], [0, 3.67], [0, 3.0], [0, 4.0], [0, 3.0], [0, 3.67], [0, 3.0], [0, 3.0], [4.0, 0], [0, 3.67], [0, 3.0], [0, 3.0], [0, 4.0], 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*/

我想找出每个子列表的平均值。为此，我做了这件事：

gpa = [[mean(sub_list) for sub_list in list] for list in grades]

但问题是，有些子列表的值为0.0，当然，代码会考虑它。当这些0.0出现时，我是否可以忽略它们，并根据其余的值计算平均值？基于这个列表，我每个子列表只有2个值，但也有其他元素在其中包含4个和5个元素。这是至关重要的事情，我正在计算，这就是为什么我需要这0是根本不考虑。

我使用的是统计平均值

Answer 1

查看您的输入列表grades，有一些子列表，其中所有值都等于零。如果过滤所有零，mean函数将抛出一个错误。

一种解决方案是，如果所有值都被过滤掉，则提供默认值为零。

例如：

gpa = [[mean([i for i in sub_list if i!=0] or [0]) for sub_list in list] for list in grades]
print(gpa)

指纹：

[[3.5, 3.0, 3.5, 3.33, 3.0, 3.835, 3.335, 3.5, 3.665, 3.665, 3.0, 3.67, 3.165, 3.5, 3.335, 3.665, 3.665, 4.0, 3.335, ...

... and so on (without throwing an error)

Answer 2

首先，您的平均值不会受到零值的影响。

第二，如果你忽略了零，那么，你会在均值公式(均值=和(X)/ (n - no_of_zeros) )中减少除数吗？

如果您需要第二件事，那么，使用your_list.count(0)并从列表的长度(即len(your_list) )中减去它。

这样，您就可以真正忽略零。

Answer 3

如果您可以使用numpy，请尝试下面的代码。它既简单又快捷。我将零替换为np.nan，并使用nanmean，它返回除np.nan以外的值平均值。

import numpy as np
grades = np.array(grades)
grades[grades == 0] = np.nan
np.nanmean(grades, axis = 1)