"bambam" <[EMAIL PROTECTED]> writes: > Is it safe to write > A = [x for x in A if x in U] > or is that undefined? I understand that the slice operation > can be used to make a temporary copy, so I could write > A=[x for x in A[:] if x in U] > but I've just copied that without any understanding.
You get a temporary copy either way; note you're going to linearly search U on every pass. Maybe you want: SU = set(u) A = [a for x in A if x in SU] or possibly A = list(set(A) & set(U)) which will remove duplicate elements from A and not necessarily keep them in the same order, but is likely to be fastest of the bunch. -- http://mail.python.org/mailman/listinfo/python-list
