How can I unite some elems in the list?

[Mike Ru]

I have resolved it so:

list_ = ['did', 'is', 'not', 'come', 'will', 'kill', 'are', 'not']
for x in list_:
   if x == 'not':
       something = list_.index(x) -1
       newelem = list_[one] + ' not'
       list_.pop(one)
       list_.remove(x)
       list_.insert(one, newelem)
print(list_)