如何根据类似的值和键对python字典进行排序？

Question

In my case, i have a random values of dictionary like this :

dict = {2: 1, 27: 28, 56: 28, 57: 29, 58: 29, 59: 29, 28: 29, 29: 1, 30: 1, 31: 1}

if i illustrate that dictionary into hierarchy chart, it will be like this :

my goal are to sorting that dictionary sequenced by its values than following by similar keys in parallel into a list. for example, if we start from keys = 27, so the result will be like this :

list = [ 27, 28, 29, 1 ]

is there any idea to solve this problem or whether python has a capabilities library to solve it ?

Answer 1

What are you looking seems to be the path to the root where each key in the dictionary maps to its parent. Using a generator function the problem can be solved easily:

d = {2: 1, 27: 28, 56: 28, 57: 29, 58: 29, 59: 29, 28: 29, 29: 1, 30: 1, 31: 1}

def path_to_root(d, start):
    yield start
    while start in d:
        start = d[start]
        yield start

print list(path_to_root(d, 27))

Result:

[27, 28, 29, 1]