Thank you very much for further improving the code. As I understand it, the trick is to use temporary variables to minimize access time. Learned something new.

I adapted your patch to python 2.7 again. Now, in python3, the new code is even faster than the old one (sometimes) for front insertions:

36 time for 10000 insertions at front: 0.117563
opt36 time for 10000 insertions at front: 0.116014

36 time for 10000 insertions at front: 0.114282
opt36 time for 10000 insertions at front: 0.116710

old time for 5000 insertions at front: 0.044055
new time for 5000 insertions at front: 0.075433
opt27 time for 5000 insertions at front: 0.052135

old time for 5000 insertions at back: 15.241450
new time for 5000 insertions at back: 0.071004
opt27 time for 5000 insertions at back: 0.046850

I hope you can consider, the patch for python 2.7. There the performance gain is most significant.