SortedDict：按python中的值排序

Question

SortedDict is a class that inherits from dictionary and keeps elements sorted by key all the time. We can also specify for it to sort by some function of the key as follows.

def func(x):
    return -x

sd = SortedDict(func)

However, I would like to have it sort by values of the dictionary. For example:

d = {0:[34, 67, 3],1:[12, 4, 9],2:[25, 3, 1]}

I want this to be sorted by the first element of each array, so that I have a sorted dict as follows:

sd = {1:[12, 4, 9],2:[25, 3, 1],0:[34, 67, 3]}

Is there a way for me to do it? If I do the following:

def func(x):
   return d[x][0]

this is not a permanant solution, because, if I update my sorted dictionary:

sd.update({4:[6,5,9]})

I get a key error from the original dictionary.

I need a way for the function to access the value of the key in sd itself. Would this be possible?

Answer 1

I believe you cannot order dictionaries. If you want to maintain an ordering with the key, maybe go for an array of arrays with your key in the first or last position. You can use the sorted function to sort the dictionary but it will not give you a dictionary object back in order

d = {0:[34, 67, 3],1:[12, 4, 9],2:[25, 3, 1]}
d_sorted = sorted(d.items(), key=lambda kv: kv[1][0])

which returns

[(1, [12, 4, 9]), (2, [25, 3, 1]), (0, [34, 67, 3])]