[Python-Dev] [Python-checkins] cpython: whatsnew: XMLPullParser, plus some doc updates. (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Mon Jan 6 16:22:21 CET 2014

On 5 Jan 2014 12:54, "r.david.murray" <python-checkins at python.org> wrote:

http://hg.python.org/cpython/rev/069f88f4935f changeset: 88308:069f88f4935f user: R David Murray <rdmurray at bitdance.com> date: Sat Jan 04 23:52:50 2014 -0500 summary: whatsnew: XMLPullParser, plus some doc updates. I was confused by the text saying that readevents "iterated", since it actually returns an iterator (that's what a generator does) that the caller must then iterate. So I tidied up the language. I'm not sure what the sentence "Events provided in a previous call to readevents() will not be yielded again." is trying to convey, so I didn't try to fix that.

It's a mutating API - once the events have been retrieved, that's it, they're gone from the internal state. Suggestions for wording improvements welcome :)

Cheers, Nick.

Also fixed a couple more news items. files: Doc/library/xml.etree.elementtree.rst | 23 +++++++++----- Doc/whatsnew/3.4.rst | 7 ++- Lib/xml/etree/ElementTree.py | 2 +- Misc/NEWS | 12 +++--- 4 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst --- a/Doc/library/xml.etree.elementtree.rst +++ b/Doc/library/xml.etree.elementtree.rst @@ -105,12 +105,15 @@ >>> root[0][1].text '2008' + +.. elementtree-pull-parsing: + Pull API for non-blocking parsing ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Most parsing functions provided by this module require to read the whole -document at once before returning any result. It is possible to use a -:class:XMLParser and feed data into it incrementally, but it's a push API that +Most parsing functions provided by this module require the whole document +to be read at once before returning any result. It is possible to use an +:class:XMLParser and feed data into it incrementally, but it is a push API that calls methods on a callback target, which is too low-level and inconvenient for most needs. Sometimes what the user really wants is to be able to parse XML incrementally, without blocking operations, while enjoying the convenience of @@ -119,7 +122,7 @@ The most powerful tool for doing this is :class:XMLPullParser. It does not require a blocking read to obtain the XML data, and is instead fed with data incrementally with :meth:XMLPullParser.feed calls. To get the parsed XML -elements, call :meth:XMLPullParser.readevents. Here's an example:: +elements, call :meth:XMLPullParser.readevents. Here is an example:: >>> parser = ET.XMLPullParser(['start', 'end']) >>> parser.feed('sometext') @@ -1038,15 +1041,17 @@ .. method:: readevents() - Iterate over the events which have been encountered in the data fed to the - parser. This method yields (event, elem) pairs, where event is a + Return an iterator over the events which have been encountered in the + data fed to the + parser. The iterator yields (event, elem) pairs, where event is a string representing the type of event (e.g. "end") and elem is the encountered :class:Element object. Events provided in a previous call to :meth:readevents will not be - yielded again. As events are consumed from the internal queue only as - they are retrieved from the iterator, multiple readers calling - :meth:readevents in parallel will have unpredictable results. + yielded again. Events are consumed from the internal queue only when + they are retrieved from the iterator, so multiple readers iterating in + parallel over iterators obtained from :meth:readevents will have + unpredictable results. .. note:: diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst --- a/Doc/whatsnew/3.4.rst +++ b/Doc/whatsnew/3.4.rst @@ -1088,9 +1088,10 @@ xml.etree --------- -Add an event-driven parser for non-blocking applications, -:class:~xml.etree.ElementTree.XMLPullParser. -(Contributed by Antoine Pitrou in :issue:17741.) +A new parser, :class:~xml.etree.ElementTree.XMLPullParser, allows a +non-blocking applications to parse XML documents. An example can be +seen at :ref:elementtree-pull-parsing. (Contributed by Antoine +Pitrou in :issue:17741.) The :mod:xml.etree.ElementTree :func:~xml.etree.ElementTree.tostring and :func:~xml.etree.ElementTree.tostringlist functions, and the diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py --- a/Lib/xml/etree/ElementTree.py +++ b/Lib/xml/etree/ElementTree.py @@ -1251,7 +1251,7 @@ self.closeandreturnroot() def readevents(self): - """Iterate over currently available (event, elem) pairs. + """Return an iterator over currently available (event, elem) pairs. Events are consumed from the internal event queue as they are retrieved from the iterator. diff --git a/Misc/NEWS b/Misc/NEWS --- a/Misc/NEWS +++ b/Misc/NEWS @@ -2193,14 +2193,14 @@ - Issue #17555: Fix ForkAwareThreadLock so that size of after fork registry does not grow exponentially with generation of process. -- Issue #17707: multiprocessing.Queue's get() method does not block for short - timeouts. - -- Isuse #17720: Fix the Python implementation of pickle.Unpickler to correctly +- Issue #17707: fix regression in multiprocessing.Queue's get() method where + it did not block for short timeouts. + +- Issue #17720: Fix the Python implementation of pickle.Unpickler to correctly process the APPENDS opcode when it is used on non-list objects. -- Issue #17012: shutil.which() no longer fallbacks to the PATH environment - variable if empty path argument is specified. Patch by Serhiy Storchaka. +- Issue #17012: shutil.which() no longer falls back to the PATH environment + variable if an empty path argument is specified. Patch by Serhiy Storchaka. - Issue #17710: Fix pickle raising a SystemError on bogus input. -- Repository URL: http://hg.python.org/cpython

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