def f(L):
	o=[];i=[];j=[]
	for x in L:[i,j][[]<x]+=[x]
	if i:o+=[i]
	if j:o+=f(sum(j,[]))
	return o
 
L = [1, 2, [3, [4, 5], 6, [7, [8], 9]]] # => [1, 2], [3, 6], [4, 5, 7, 9], [8]
print f(L)
 
L = [3, 1, [12, [14, [18], 2], 1], [[4]], 5] #=> [[3, 1, 5], [12, 1], [14, 2, 4], [18]]
print f(L)
 
L = [2, 1, [[5]], 6] #=> [[2, 1, 6], [5]]
print f(L)
 
L = [[54, [43, 76, [[[-19]]]], 20], 12] #=> [[12], [54, 20], [43, 76], [-19]]
print f(L)
 
L = [[[50]], [[50]]] #=> [[50, 50]]
print f(L)

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