Using a for loop might be easier to understand.
test_list=[1,3,5,7]
ctr = 0
stop=len(test_list)
for j in range(0, stop):
ctr += 1
before_add = test_list[j]
test_list[j] += ctr ## ctr = j+1 in this specific case
print "element", j, "did =", before_add, "and now =", test_list[j]
print "\n", test_list