New submission from Chris Jerdonek: > Date: Thu, 20 Sep 2012 15:14:36 -0400 > To: d...@python.org > Subject: [docs] map objects are not lists > > 5.1.3. List > Comprehensions<http://docs.python.org/dev/tutorial/datastructures.html#list-comprehensions> > > List comprehensions provide a concise way to create lists. Common > applications are to make new lists where each element is the result of some > operations applied to each member of another sequence or iterable, or to > create a subsequence of those elements that satisfy a certain condition. > > For example, assume we want to create a list of squares, like: >>>> > >>>> squares = []>>> for x in range(10):... squares.append(x**2)...>>> >>>> squares[0, 1, 4, 9, 16, 25, 36, 49, 64, 81] > > We can obtain the same result with: > > squares = [x**2 for x in range(10)] > > This is also equivalent to squares = map(lambda x: x**2, range(10)), but > it?s more concise and readable. > > > I think that the last sentence above should read: > > squares = list(map(lambda x: x**2, range(10))) > > In other words, the map function returns a map object, not a list object, > so the list() function needs to be used to convert it to something that is > truly equivalent to the previous definitions of "squares". (In case it > matters, I am using Python-3.3.0rc2 on RHEL 6.3.)
(from http://mail.python.org/pipermail/docs/2012-September/010525.html ) ---------- assignee: docs@python components: Documentation keywords: easy messages: 171405 nosy: chris.jerdonek, docs@python priority: normal severity: normal stage: needs patch status: open title: fix map() statement in list comprehension example type: enhancement versions: Python 3.3 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue16073> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com