Python: Merging lists with lists

I have a list:

packets=[['B', 'A'], ['B', 'C'], ['A', 'D'], ['C', 'D'], ['C', 'E'], ['D', 'E'], []]

I have two for loops on the same list something like:

for a in packets[:]:
   for b in packets[:]:

i.e., each time a=['B','A'] b iterates from ['B','A'] all the way to ['D','E']. This is what I want to do:

If the last element of a is equal to the first element of b i.e., when a=['B','A'] and b=['A','D'] I must have ['B','A','D']. Again the last element of ['B','A'开发者_StackOverflow,'D'] is equal to the first element of ['D','E']. So, now I must have ['B','C','D','E'].

Similarly, when A=['B','C'] and b=['C','E'] I must have ['B','C','E']. When A=['B','C'] and b=['C','D'] and b=['D','E'] I must have ['B','C','D','E'] and so on.

Any ideas?

Not sure if this is what you want, but

>>> packets=[['B', 'A'], ['B', 'C'], ['A', 'D'], ['C', 'D'], ['C', 'E'], ['D', 'E'], []]
>>> 
>>> for a in packets:
...     for b in packets:
...         if a and b and a[-1]==b[0]:
...             print a[:-1]+b
...             packets.append(a[:-1]+b)
... 
['B', 'A', 'D']
['B', 'C', 'D']
['B', 'C', 'E']
['A', 'D', 'E']
['C', 'D', 'E']
['B', 'A', 'D', 'E']
['B', 'C', 'D', 'E']