>>> students = [('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10),] 

>>> sorted(students, key=lambda student : student[2]) # sort by age 
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)] 

>>> sorted(students, cmp=lambda x,y : cmp(x[2], y[2])) # sort by age 
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)] 

>>> from operator import itemgetter, attrgetter 
>>> sorted(students, key=itemgetter(2)) 

>>> sorted(students, key=itemgetter(1,2)) # sort by grade then by age 
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)] 

>>> d = {'data1':3, 'data2':1, 'data3':2, 'data4':4} 
>>> sorted(d.iteritems(), key=itemgetter(1), reverse=True) 
[('data4', 4), ('data1', 3), ('data3', 2), ('data2', 1)] 

class itemgetter(__builtin__.object) 
| itemgetter(item, ...) --> itemgetter object 
| 
| Return a callable object that fetches the given item(s) from its operand. 
| After, f=itemgetter(2), the call f(r) returns r[2]. 
| After, g=itemgetter(2,5,3), the call g(r) returns (r[2], r[5], r[3]) 

def itemgetter(i,*a): 
 def func(obj): 
 r = obj[i] 
 if a: 
 r = (r,) + tuple(obj[i] for i in a) 
 return r 
 return func 
 
>>> a = [1,2,3] 
>>> b=operator.itemgetter(1) 
>>> b(a) 
2 
>>> b=operator.itemgetter(1,0) 
>>> b(a) 
(2, 1) 
>>> b=itemgetter(1) 
>>> b(a) 
2 
>>> b=itemgetter(1,0) 
>>> b(a) 
(2, 1)