list sort

Usage: list.sort([cmp[,key[,reverse]]])

how to use cmp parameter

def my_cmp(x,y):
  if x<y:
    return -1
  elif x==y:
    return 0
  else:
    return 1
arr = [2,5,3,1,4]
arr.sort(my_cmp)
print arr

 

 

Above example's result is [1,2,3,4,5];

how to use key parameter

arr = ['bj:beijing','sh:shanghai','sd:shandong']
arr.sort(key=lambda x: x[:2])
print arr

In above example, when sorting the list, just compare every element's first two char(bj, sh, sd).

Above example's result is ['bj:beijing', 'sd:shandong', 'sh:shanghai'];

how to use reverse value

reverse is a boolean value. If set to True , then the list elements are sorted as if each comparison were reversed. Generally sorting is in asc order, when set reverse to true, sorting will be in desc order.