OrderedDict for older versions of python

Question

Ordered dictionaries are extremely useful structures, but unfortunately these are quite recent only working in versions from 3.1 and 2.7. How can I use an ordered dictionary

Answer 1

For those who can't depend on the user having pip for some reason, here is a really terrible implementaiton of OrderedDict (it is immutable, has most of the features but none of the performance boost).

class OrderedDict(tuple):
    '''A really terrible implementation of OrderedDict (for python < 2.7)'''
    def __new__(cls, constructor, *args):
        items = tuple(constructor)
        values = tuple(n[1] for n in items)
        out = tuple.__new__(cls, (n[0] for n in items))
        out.keys = lambda: out
        out.items = lambda: items
        out.values = lambda: values
        return out

    def __getitem__(self, key):
        try:
            return next(v for (k, v) in self.items() if k == key)
        except:
            raise KeyError(key)