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[3.8] bpo-41892: Clarify that an example in the ElementTree docs explicitly avoids modifying an XML tree while iterating over it. (GH-22464) #22553

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Oct 4, 2020
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[3.8] bpo-41892: Clarify that an example in the ElementTree docs explicitly avoids modifying an XML tree while iterating over it. (GH-22464) #22553

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6 changes: 6 additions & 0 deletions Doc/library/xml.etree.elementtree.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -249,12 +249,18 @@ We can remove elements using :meth:`Element.remove`. Let's say we want to
remove all countries with a rank higher than 50::

>>> for country in root.findall('country'):
... # using root.findall() to avoid removal during traversal
... rank = int(country.find('rank').text)
... if rank > 50:
... root.remove(country)
...
>>> tree.write('output.xml')

Note that concurrent modification while iterating can lead to problems,
just like when iterating and modifying Python lists or dicts.
Therefore, the example first collects all matching elements with
``root.findall()``, and only then iterates over the list of matches.

Our XML now looks like this:

.. code-block:: xml
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