006 Python Cookbook 01-04 Finding the Largest N

#!/usr/bin/env python

# http://chimera.labs.oreilly.com/books/1230000000393/ch01.html#findingthelargestorsmallest
# Finding the Largest or Smallest N Items

import heapq def do_sth_on_list_num(inlist):     print "inlist = ", inlist     print "heapq.nlargest(3, inlist)  = ", heapq.nlargest(3, inlist)     print "heapq.nsmallest(3, inlist) = ", heapq.nsmallest(3, inlist)     print def do_sth_on_list_nested(llist):     print "llist = "     for i in llist:         print "\t", i     print     lexpensive = heapq.nlargest(1, llist, key=lambda s: s['price'] )     print "Most expensive = ", lexpensive     lpopular = heapq.nsmallest(1, llist, key=lambda s: s['userbase'] )     print "Less popular   = ", lpopular     print def do_sth_for_top2(llist):     print "llist = "     for i in llist:         print "\t", i     print     print "Most expensive = "     lexpensive = heapq.nlargest(2, llist, key=lambda s: s['price'] )     for j in lexpensive:         print "\t", j     print "Less popular   = "     lpopular = heapq.nsmallest(2, llist, key=lambda s: s['userbase'] )       for k in lpopular:         print "\t", k     print def do_sth_on_list_by_heap(inlist):     print "inlist = ", inlist     heap = list(inlist)     print "after heapq.heapify(heap)"     heapq.heapify(heap)     while len(heap) > 0:         print "\theapq.heappop(heap)", heapq.heappop(heap)     print print "----------" print "do_sth_on_list_num(list_num)" list_num = [2, 4, 6, 8, 7, 9, 5, 3, 1] do_sth_on_list_num(list_num) print "----------" print "do_sth_on_list_nested(list_list)" list_list = [     {'name': 'line', 'userbase': 100, 'price': 0 },     {'name': 'whatsapp', 'userbase': 150, 'price': 1.0 },     {'name': 'skype', 'userbase': 500, 'price': 0.99 } ] do_sth_on_list_nested(list_list) print "----------" print "do_sth_for_top2(list_list)" do_sth_for_top2(list_list) print "----------" print "do_sth_on_list_by_heap(list_num)" do_sth_on_list_by_heap(list_num)

---------- do_sth_on_list_num(list_num) inlist =  [2, 4, 6, 8, 7, 9, 5, 3, 1] heapq.nlargest(3, inlist)  =  [9, 8, 7] heapq.nsmallest(3, inlist) =  [1, 2, 3] ---------- do_sth_on_list_nested(list_list) llist = {'price': 0, 'userbase': 100, 'name': 'line'} {'price': 1.0, 'userbase': 150, 'name': 'whatsapp'} {'price': 0.99, 'userbase': 500, 'name': 'skype'} Most expensive =  [{'price': 1.0, 'userbase': 150, 'name': 'whatsapp'}] Less popular   =  [{'price': 0, 'userbase': 100, 'name': 'line'}] ---------- do_sth_for_top2(list_list) llist = {'price': 0, 'userbase': 100, 'name': 'line'} {'price': 1.0, 'userbase': 150, 'name': 'whatsapp'} {'price': 0.99, 'userbase': 500, 'name': 'skype'} Most expensive = {'price': 1.0, 'userbase': 150, 'name': 'whatsapp'} {'price': 0.99, 'userbase': 500, 'name': 'skype'} Less popular   = {'price': 0, 'userbase': 100, 'name': 'line'} {'price': 1.0, 'userbase': 150, 'name': 'whatsapp'} ---------- do_sth_on_list_by_heap(list_num) inlist =  [2, 4, 6, 8, 7, 9, 5, 3, 1] after heapq.heapify(heap) heapq.heappop(heap) 1 heapq.heappop(heap) 2 heapq.heappop(heap) 3 heapq.heappop(heap) 4 heapq.heappop(heap) 5 heapq.heappop(heap) 6 heapq.heappop(heap) 7 heapq.heappop(heap) 8 heapq.heappop(heap) 9