lotrpy <[EMAIL PROTECTED]> writes: > if i want sort each line by the first part,(it's a integer, in fact). > don't know how to do it with itemgetter. > key = int(itemgetter(0)) is wrong, key = lambda x:int(x[0]) works. > but s.b. told me itemgetter execute more quickly .
Use lambda when it works better for you, the speed difference is marginal in practice anyway. itemgetter is not (and was never intended to be) a general substitute for functions, as you've discovered. The marginal speed difference between itemgetter and an explicit lambda that does the subscripts is a consequence of itemgetter being written in C, meaning it avoids the creation of a Python stack frame, etc. Combining int(...) with this operation requires coding the key function in Python, which removes itemgetter's advantage. In other words, you cannot retain itemgetter's speed advantage with more complex keys. If the sorting performance is a problem for you, please give more details about what you're doing -- there might be better ways to speed up the code. -- http://mail.python.org/mailman/listinfo/python-list
