Question

I have a 2D dictionary in python indexed by two IPs. I want to group the dictionary by the first key.

For example, the before would look like this:

myDict["182.12.17.50"]["175.12.13.14"] = 14
myDict["182.15.12.30"]["175.12.13.15"] = 10
myDict["182.12.17.50"]["185.23.15.69"] = 30
myDict["182.15.12.30"]["145.33.34.56"] = 230

so

for key1, key2 in myDict:
     print key1 +"   " +key2 +"   " +myDict[key1, key2]

would print

182.12.17.50   175.12.13.14   14
182.15.12.30   175.12.13.15   10
182.12.17.50   185.23.15.69   30
182.15.12.30   145.33.34.56   230

But I want to sort it so it would print

182.12.17.50   175.12.13.14   14
182.12.17.50   185.23.15.69   30
182.15.12.30   175.12.13.15   10
182.15.12.30   145.33.34.56   230

Any idea how this could be accomplished?

Answer 1

Well, there are a variety of options. One of them would be to sort the keys before printing, something like this:

for key1 in sorted(myDict):
    for key2 in myDict[key1]:
        print key1 +"   " +key2 +"   " +myDict[key1][key2]

Another option would be to use the sorteddict class from the blist module (disclaimer: I’m the author 🙂 ), which will always return the keys in sorted order.

In either cases, since the keys are IP addresses, you might want to write a custom “key” function to pass to sort/sorted/sorteddict so they will sorted by their numeric value rather than lexicographically as a string.