python - Group objects with an identical list attribute -

i have 2 classes:

class a:    def __init__(self, name, li):       self.b_list = li  class b:    def __init__(self, i):       self.i = 

class a contains list of objects of type class b.

assuming have list of class a objects, how can group class a objects have identical b_list together?

for example:

a_list = []  li = [b(1), b(2), b(3)] a_list.append(a(li))  li = [b(2), b(3)] a_list.append(a(li))  li = [b(1), b(2), b(3)] a_list.append(a(li)) 

after processing should give 2 lists, 1 list first , third a, , list second a. or in nutshell:

result = [    [ a([b(1),b(2),b(3)]), a([b(1),b(2),b(3)]) ],    [ a([b(2),b(3)] ] ] 

for starters, i've removed name parameter class a, since rest of details omitted it.

to group class objects together, you're going need define meant when 2 objects equal. i've created __cmp__ method let sort on objects comparing them.

now, since objects composed of b objects, you're going need define meant 2 b objects being equal. i've created __eq__ method in class b that.

next, i've sorted instances make grouping them easier, , added __str__ method class a, , __repr__ method class b can verify being grouped correctly.

i haven't added error checking anywhere, code little fragile.

class a:     def __init__(self, li):         self.b_list = li      def __cmp__(self, other):         return cmp([elem.i elem in self.b_list],                     [elem.i elem in other.b_list])      def __str__(self):         return "a({})".format(self.b_list)  class b:     def __init__(self, i):        self.i =      def __eq__(self, other):        return self.i == other.i      def __repr__(self):         return "b({})".format(self.i)  def main():      a_list = []      li = [b(1), b(2), b(3)]     a_list.append(a(li))      li = [b(2), b(3)]     a_list.append(a(li))      li = [b(1), b(2), b(3)]     a_list.append(a(li))      result = []     last_item = none     item in sorted(a_list):         if last_item , item == last_item:             result[-1] = result[-1] + [item]         else:             result.append([item])         last_item = item      row in result:         print [str(elem) elem in row]  if __name__ == '__main__':     main() 

result:

['a([b(1), b(2), b(3)])', 'a([b(1), b(2), b(3)])'] ['a([b(2), b(3)])']