sort Python list with two keys but only one in reverse order

Question

I was wondering what would be a Pythonic way of sorting a list of tuples by two keys whereby sorting with one (and only one) key would be in a reverse order and sorting with the the other would be case insensitive. More specifically, I have a list containing tuples like:

myList = [(ele1A, ele2A),(ele1B, ele2B),(ele1C, ele2C)] 

I can use the following code to sort it with two keys:

sortedList = sorted(myList, key = lambda y: (y[0].lower(), y[1])) 

To sort in reverse order I can use

sortedList = sorted(myList, key = lambda y: (y[0].lower(), y[1]), reverse = True) 

But this would sort in a reverse order with two keys.

Answer 1

Two keys will be used when we need to sort a list with two constraints one in ascending order and other in descending in the same list or any
In your example
sortedList = sorted(myList, key = lambda y: (y[0].lower(), y[1])) can sort entire list only in one order
you can try these and check whats happening

sortedList = sorted(myList, key = lambda y: (y[0].lower(), -y[1])) sortedList = sorted(myList, key = lambda y: (-y[0].lower(), y[1])) sortedList = sorted(myList, key = lambda y: (-y[0].lower(), -y[1])) 

hope you will understand after this ;)

Answer 2

You could create a reversor class and use it to decorate the key in question. This class could be used to reverse any field that is comparable.

class reversor:     def __init__(self, obj):         self.obj = obj      def __eq__(self, other):         return other.obj == self.obj      def __lt__(self, other):         return other.obj < self.obj 

Use it like so:

sortedList = sorted(myList, key=lambda(y): (y[0].lower(), reversor(y[1])))