Java's TreeSet equivalent in Python?

The Python 2.7 docs for collections.OrderedDict has a link to a OrderedDict recipe that runs on Python 2.4 or better.

Edit: In regard to sorting: Use key= rather than cmp=. It tends to lead to faster code and moreover, the cmp= keyword has been eliminated in Python3.

d={5:6,7:8,100:101,1:2,3:4}
print(d.items())
# [(1, 2), (3, 4), (100, 101), (5, 6), (7, 8)]

The code you posted for mycmp doesn't make it clear what you want passed as x1. Below, I assume x1 is supposed to be the value in each key-value pair. If so, you could do something like this:

length=4
print(sorted(d.items(),key=lambda item: abs(item[1]-length) ))
# [(3, 4), (1, 2), (5, 6), (7, 8), (100, 101)]

key=... is passed a function, lambda item: abs(item[1]-length). For each item in d.items(), the lambda function returns the number abs(item[1]-length). This number acts as proxy for the item as far as sorting is concerned. See this essay for more information on sorting idioms in Python.

PS. len is a Python builtin function. So as to not clobber that len, I've changed the variable name to length.

I recently implemented TreeSet for Python using bisect module.

https://github.com/fukatani/TreeSet

Its usage is similar to Java's Treeset.

ex.

from treeset import TreeSet
ts = TreeSet([3,7,2,7,1,3])
print(ts)
>>> [1, 2, 3, 7]

ts.add(4)
print(ts)
>>> [1, 2, 3, 4, 7]

ts.remove(7)
print(ts)
>>> [1, 2, 3, 4]

print(ts[2])
>>> 3

I'd need to see some example data, but if you're just trying to do a weighted sort, then the builtin python sorted() can do it, two ways.

With well ordered tuples and a key() function:

def cost_per_page(book):
    title, pagecount, cost = book
    return float(cost)/pagecount

booklist = [
        ("Grey's Anatomy", 3000, 200),
        ('The Hobbit', 300, 7.25),
        ('Moby Dick', 4000, 4.75),
]
for book in sorted(booklist, key=cost_per_page):
    print book

or with a class with a __cmp__ operator.

class Book(object):
    def __init__(self, title, pagecount, cost):
        self.title = title
        self.pagecount = pagecount
        self.cost = cost
    def pagecost(self):
        return float(self.cost)/self.pagecount
    def __cmp__(self, other):
        'only comparable with other books'
        return cmp(self.pagecost(), other.pagecost())
    def __str__(self):
        return str((self.title, self.pagecount, self.cost))

booklist = [
        Book("Grey's Anatomy", 3000, 200),
        Book('The Hobbit', 300, 7.25),
        Book('Moby Dick', 4000, 4.75),
]
for book in sorted(booklist):
    print book

Both of these return the same output:

('Moby Dick', 4000, 4.75)
('The Hobbit', 300, 7.25)
("Grey's Anatomy", 3000, 200)