Why two -for- can rebound the variable and give this output?

URL:
https://www.edx.org/courses/MITx/6.00x/2012_Fall/discussion/forum/600x_l3_v3/threads/5077eff65308862b00000059

Question

Why two -for- can rebound the variable and give this output?

URL:
https://www.edx.org/courses/MITx/6.00x/2012_Fall/discussion/forum/600x_l3_v3/threads/5077eff65308862b00000059

anonymous · Answer

because when you go to the first loop - python created sequence (0, 1, 2, 3). And on the next iteration doesn't check ui value. in the second loop - first time you have ui = 4 and after that - 2