Enforce items at beginning and end of list

Question

How can I modify this list so that all p\'s appear at the beginning, the q\'s at the end, and the values in between are sorted alphabetically?

Answer 1

You can find all p and q elements, filter the original list, and then sort:

l = ['f','g','p','a','p','c','b','q','z','n','d','t','q']
_ps, _qs = [i for i in l if i == 'p'], [i for i in l if i == 'q']
new_l = _ps+sorted(filter(lambda x:x not in {'q', 'p'}, l))+_qs

Output:

['p', 'p', 'a', 'b', 'c', 'd', 'f', 'g', 'n', 't', 'z', 'q', 'q']