python - List comprehension with several elements per entry -

this 1 clear:

a = ['a', 'b', 'c'] x = [v v in a] 

but not sure how this:

sep = 5 # ??? y = [v + sep v in a] print y # expected ['a', 5, 'b', 5, 'c', 5] 

how can write list comprehension multiple elements per source element?

i not interested in optimizations of code: please not refer [:] operator or join method or on lines. code needs list comprehension. alternative have @ moment 4 lines for loop, inconvenient:

y = [] v in a:     y.append(v)     y.append(sep) 

using nested list comprehension:

>>> = ['a','b','c'] >>> [item  x in item in (x, 5)] ['a', 5, 'b', 5, 'c', 5]