python中字典中的气泡排序

Question

I am trying to do bubble sort in descending order

input={"m":1,"i":4,"s":4,"P":2}

output={"i":4,"s":4,"p":2,"m":1}

but a type error occurs. How can I do this?

Below is the code:

dict={"m":1,"i":4,"s":4,"P":2}
for key,value in dict.items():
    if(dict[key]<dict[key+1]):
        temp=dict[key]
        dict[key]=dict[key+1]
        dict[key+1]=temp
print(dict)        

Answer 1

A dictionary has no order : if you add/remove/update elements in a dictionary, the order in which the keys are iterated can change.

So you can not "sort" a dictionary. What you can do however, is for example sort a list of 2-tuples , like:

my_list = list(my_dict.items())

We then retrieve:

>>> my_list
[('m', 1), ('i', 4), ('s', 4), ('P', 2)]

and thnen we can sort the list (for example with bubblesort) like:

for mx in range(len(my_list)-1, -1, -1):
    swapped = False
    for i in range(mx):
        if my_list[i][1] < my_list[i+1][1]:
            my_list[i], my_list[i+1] = my_list[i+1], my_list[i]
            swapped = True
    if not swapped:
        break

Then afterwards, we have:

>>> my_list
[('i', 4), ('s', 4), ('P', 2), ('m', 1)] 

Answer 2

do you mean something like this?

dict={"m":1,"i":4,"s":4,"P":2}
sorted_values = sorted(dict.values(),reverse = True)
print sorted_values

But this isn't "manual" bubble sort. So if you have to to bubble sort this by your own just use the list of values via

values = dict.values()

And then sort them ;)

As timgeb already mentioned in a comment, I'm sorry didnt see the comment before I wrote this post.