Python利用operator模块实现对象的多级排序详解

class A(object):
 def __init__(self, b):
  self.b = b
 def __str__(self):
  return "[%s, %s, %s]" % (self.b.attr1, self.b.attr2, self.b.attr3)
 def __repr__(self):
  return "[%s, %s, %s]" % (self.b.attr1, self.b.attr2, self.b.attr3)

class B(object):
 def __init__(self, attr1, attr2, attr3):
  self.attr1 = attr1
  self.attr2 = attr2
  self.attr3 = attr3
 def __str__(self):
  return "[%s, %s, %s]" % (self.attr1, self.attr2, self.attr3)
 def __repr__(self):
  return "[%s, %s, %s]" % (self.attr1, self.attr2, self.attr3)

from operator import itemgetter, attrgetter

a1 = A(B('u1', 'AAA', 100))
a2 = A(B('u2', 'BBB', 100))
a3 = A(B('u3', 'BBB', 10))
aaa = (a1, a2, a3,)

print sorted(aaa, key=attrgetter('b.attr2', 'b.attr3'))
print sorted(aaa, key=attrgetter('b.attr2', 'b.attr3')， reverse=True)

[[u1, AAA, 100], [u3, BBB, 10], [u2, BBB, 100]]
[[u2, BBB, 100], [u3, BBB, 10], [u1, AAA, 100]]

s = sorted(aaa, key=attrgetter('b.attr3'), reverse=True)
s = sorted(s, key=attrgetter('b.attr2'))
print s

[[u1, AAA, 100], [u2, BBB, 100], [u3, BBB, 10]]