In Python, How can I get the next and previous key:value of a particular key in a dictionary?

Question

Okay, so this is a little hard to explain, but here goes:

I have a dictionary, which I'm adding content to. The content is a hashed username (key) with an IP address (value). I was putting the hashes into an order by running them against base 16, and then using Collection.orderedDict. So, the dictionary looked a little like this:

d = {'1234': '8.8.8.8', '2345':'0.0.0.0', '3213':'4.4.4.4', '4523':'1.1.1.1', '7654':'1.3.3.7', '9999':'127.0.0.1'}

What I needed was a mechanism that would allow me to pick one of those keys, and get the key/value item one higher and one lower. So, for example, If I were to pick 2345, the code would return the key:value combinations '1234:8.8.8.8' and '3213:4.4.4.4'

So, something like:

for i in d:
  while i < len(d)
   if i == '2345':
     print i.nextItem
     print i.previousItem
     break()

Answer 1

Edit: OP now states that they are using OrderedDicts but the use case still requires this sort of approach.

Since dicts are not ordered you cannot directly do this. From your example, you are trying to reference the item like you would use a linked list.

A quick solution would be instead to extract the keys and sort them then iterate over that list:

keyList=sorted(d.keys())
for i,v in enumerate(keyList):
    if v=='eeee':
        print d[keyList[i+1]]
        print d[keyList[i-1]]

The keyList holds the order of your items and you have to go back to it to find out what the next/previous key is to get the next/previous value. You also have to check for i+1 being greater than the list length and i-1 being less than 0.

You can use an OrderedDict similarly but I believe that you still have to do the above with a separate list as OrderedDict doesn't have next/prev methods.