yoba = [(None, None), (None, 'Smack my Bitch Up'), ('The Prodigy', None), ('The Prodigy', 'Smack my Bitch Up')]

def dologic(A, B):
    
    if None in (A, B):
    	
    	return A or B or "..."
    	
    else:
    	
    	return str.format("{} - {}", A, B)
        
for A, B in yoba:
    print(dologic(A, B))