Rant (was Re: x*x if x>10

[ssecorp]

I might be misunderstanding OP but:

a+b+c+d+e is simple way of concatenating 5 lists...

as a function that takes any amount of lists and concatenates them:
def concat(*args):
	c = []
	for elem in args:
		c += elem
	return c

don't know if extend is faster or slower or the same as + :

def concat(*args):
	c = []
	for elem in args:
		c.extend(elem)
	return c

I don't know of a built-in.