Python 2.5 dictionary 2 key sort

Question

I have a dictionary of 200,000 items (the keys are strings and the values are integers).

What is the best/most pythonic way to print the items sorted by descending v

Answer 1

You can't sort dictionaries. You have to sort the list of items.

Previous versions were wrong. When you have a numeric value, it's easy to sort in reverse order. These will do that. But this isn't general. This only works because the value is numeric.

a = { 'key':1, 'another':2, 'key2':1 }

b= a.items()
b.sort( key=lambda a:(-a[1],a[0]) )
print b

Here's an alternative, using an explicit function instead of a lambda and the cmp instead of the key option.

def valueKeyCmp( a, b ):
    return cmp( (-a[1], a[0]), (-b[1], b[0] ) )

b.sort( cmp= valueKeyCmp )
print b

The more general solution is actually two separate sorts

b.sort( key=lambda a:a[1], reverse=True )
b.sort( key=lambda a:a[0] )
print b