[Richard] > I know I can use a 'for' loop and create two new lists > using 'newList1.append(x)', etc. Is there an efficient way > to create these two new lists without using a slow for loop?
If trying to optimize before writing and timing code, then at least validate your assumptions. In Python, for-loops are blazingly fast. They are almost never the bottleneck. Python is not Matlab -- "vectorizing" for-loops only pays-off when a high-speed functional happens to exactly match you needs (in this case, zip() happens to be a good fit). Even when a functional offers a speed-up, much of the gain is likely due to implementation specific optimizations which allocate result lists all at once rather than building them one at time. Also, for all but the most simple inner-loop operations, the for-loop overhead almost always dominated by the time to execute the operation itself. Executive summary: Python's for-loops are both elegant and fast. It is a mistake to habitually avoid them. Raymond -- http://mail.python.org/mailman/listinfo/python-list
