gistfile1.py

from collections import defaultdict

def sorter_second_desc(x,y):
    """for sorting list of pairs by the second element, descending.
    e.g. count""" 
    return -1 * cmp(x[1], y[1])

def main():
    sentence='the quick brown FOX JumpeD Over the lazy dog'
    
    charCount=defaultdict(int) #int factory default is 0
    for ch in sentence.lower():
        charCount[ch]+=1
    
    items = charCount.items()
    items.sort(sorter_second_desc)
    print items