Python 3.4-如何获取字典值的平均值? [英] Python 3.4 - How to get the average of dictionary values?

问题描述

我有以下字典:

StudentGrades = {
    'Ivan': [4.32, 3, 2],
    'Martin': [3.45, 5, 6],
    'Stoyan': [2, 5.67, 4],
    'Vladimir': [5.63, 4.67, 6]
}

我想创建一个函数，以打印学生的平均成绩，即值的平均值，但是我不知道如何.你能帮我吗?

I want to make a function that prints the average of the grades of the students, i.e. the average of the values, but I have no idea how. Can you help me please?

推荐答案

此答案适用于Python2，即已死

好的，所以让我们遍历所有字典键并对项目取平均值:

Okay, so let's iterate over all dictionary keys and average the items:

avgDict = {}
for k,v in StudentGrades.iteritems():
    # v is the list of grades for student k
    avgDict[k] = sum(v)/ float(len(v))

在Python3中，不再需要iteritems()方法，可以直接使用items().

In Python3, the iteritems() method is no longer necessary, can use items() directly.

现在您可以看到:

avgDict
Out[5]: 
{'Ivan': 3.106666666666667,
 'Martin': 4.816666666666666,
 'Stoyan': 3.89,
 'Vladimir': 5.433333333333334}

---

从您的问题来看，我认为您对字典的迭代感到不满意，因此输出与列表相同:

---

From your question I think you're queasy about iteration over dicts, so here is the same with output as a list :

avgList = []
for k,v in StudentGrades.iteritems():
    # v is the list of grades for student k
    avgDict.append(sum(v)/ float(len(v)))

但是要小心:不能保证在字典中的项目顺序；这就是说，不能保证在字典上打印或迭代时键/值的顺序(因为字典是未排序的"). 虽然可以保证在相同的相同字典对象(无添加/删除)上循环两次，但它们的行为相同.

Be careful though : the order of items in a dictionary is NOT guaranteed; this is, the order of key/values when printing or iterating on the dictionary is not guaranteed (as dicts are "unsorted"). Looping over the same identical dictionary object(with no additions/removals) twice is guaranteed to behave identically though.

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