Chris Angelico <ros...@gmail.com> wrote: > # Snapshot of keys: > for k in list(d): > if f(k): del d[k] > > No extra loop at the end, no switching out and in of contents, just > one little change in the loop header. Obviously you don't want to do > this when you're deleting two out of three billion, but for smallish > dicts, that won't make a visible change.
Even if you have three billion keys, the extra memory needed to create a list that references those keys is going to be a lot less than the memory used by the keys themselves. For example if the keys are 6 character strings then each string needs I think at least 45 bytes (64 bit Python 2.x, up to double that in Python 3.x) but the list only needs one 8 byte pointer per key. I would always choose this simple solution until such time as it is proved to be a problem. -- Duncan Booth -- https://mail.python.org/mailman/listinfo/python-list