>>> aa = ['a0', 'b1', 'c2', 'd3', 'e4', 'f5', 'g6', 'h7', 'i8', 'j9', 'k10', 'l11']
>>> an = []
>>> for jk in range(3, 9, 2): an.append(aa.pop(jk))
... 
>>> an
['d3', 'g6', 'j9']
>>> aa
['a0', 'b1', 'c2', 'e4', 'f5', 'h7', 'i8', 'k10', 'l11']
>>> 

***
I expect aa to be 
['a0', 'b1', 'c2', 'e4', 'g6', 'i8', 'k10', 'l11']
and an to be
['d3', 'f5', 'h7']