classification
Title: fix map() statement in list comprehension example
Type: enhancement Stage: resolved
Components: Documentation Versions: Python 3.2, Python 3.3
process
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: chris.jerdonek Nosy List: chris.jerdonek, docs@python, inglesp, python-dev
Priority: normal Keywords: easy, patch

Created on 2012-09-28 03:50 by chris.jerdonek, last changed 2012-09-28 14:30 by chris.jerdonek. This issue is now closed.

Files
File name Uploaded Description Edit
issue16073.patch inglesp, 2012-09-28 13:28 review
Messages (5)
msg171405 - (view) Author: Chris Jerdonek (chris.jerdonek) * (Python committer) Date: 2012-09-28 03:50
> Date: Thu, 20 Sep 2012 15:14:36 -0400
> To: docs@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 )
msg171459 - (view) Author: Peter Inglesby (inglesp) * Date: 2012-09-28 13:28
Have attached a patch with suggested update.

Have also grepped for similar issues elsewhere in documentation, and haven't found anything, but may have missed something.
msg171468 - (view) Author: Chris Jerdonek (chris.jerdonek) * (Python committer) Date: 2012-09-28 13:58
2.7 is not affected.
msg171474 - (view) Author: Roundup Robot (python-dev) (Python triager) Date: 2012-09-28 14:26
New changeset 6c96878eb729 by Chris Jerdonek in branch '3.2':
Close issue #16073: fix map() example in list comprehension documentation.
http://hg.python.org/cpython/rev/6c96878eb729

New changeset 8a4a88b1e964 by Chris Jerdonek in branch 'default':
Close issue #16073: merge fix from 3.2.
http://hg.python.org/cpython/rev/8a4a88b1e964
msg171476 - (view) Author: Chris Jerdonek (chris.jerdonek) * (Python committer) Date: 2012-09-28 14:30
Thanks for helping with the patch and search, Peter.
History
Date User Action Args
2012-09-28 14:30:14chris.jerdoneksetstatus: open -> closed
resolution: fixed
messages: + msg171476

stage: needs patch -> resolved
2012-09-28 14:26:09python-devsetnosy: + python-dev
messages: + msg171474
2012-09-28 13:58:46chris.jerdoneksetassignee: docs@python -> chris.jerdonek
messages: + msg171468
versions: + Python 3.2
2012-09-28 13:28:52inglespsetfiles: + issue16073.patch

nosy: + inglesp
messages: + msg171459

keywords: + patch
2012-09-28 03:50:23chris.jerdonekcreate