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Diffstat (limited to 'doc/tutorial.txt')
| -rw-r--r-- | doc/tutorial.txt | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/doc/tutorial.txt b/doc/tutorial.txt index 8ae11d86..778b5a59 100644 --- a/doc/tutorial.txt +++ b/doc/tutorial.txt @@ -861,8 +861,28 @@ element, but you can control this through the ``events`` keyword argument: Note that the text, tail and children of an Element are not necessarily there yet when receiving the ``start`` event. Only the ``end`` event guarantees -that the Element has been parsed completely. It also allows to ``clear()`` or -modify the content of an Element to save memory. +that the Element has been parsed completely. + +It also allows to ``.clear()`` or modify the content of an Element to +save memory. So if you parse a large tree and you want to keep memory +usage small, you should clean up parts of the tree that you no longer +need: + +.. sourcecode:: pycon + + >>> some_file_like = StringIO( + ... "<root><a><b>data</b></a><a><b/></a></root>") + + >>> for event, element in etree.iterparse(some_file_like): + ... if element.tag == 'b': + ... print element.text + ... elif element.tag == 'a': + ... print "** cleaning up the subtree" + ... element.clear() + data + ** cleaning up the subtree + None + ** cleaning up the subtree If memory is a real bottleneck, or if building the tree is not desired at all, the target parser interface of ``lxml.etree`` can be used. It creates |