minidom error

[txomon]

BPO	16890
Nosy	@ezio-melotti

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2013-01-08.03:24:29.332>
created_at = <Date 2013-01-08.02:58:47.283>
labels = ['expert-XML', 'type-bug', 'invalid']
title = 'minidom error'
updated_at = <Date 2013-01-08.11:07:20.382>
user = 'https://bugs.python.org/txomon'

bugs.python.org fields:

activity = <Date 2013-01-08.11:07:20.382>
actor = 'txomon'
assignee = 'none'
closed = True
closed_date = <Date 2013-01-08.03:24:29.332>
closer = 'ezio.melotti'
components = ['XML']
creation = <Date 2013-01-08.02:58:47.283>
creator = 'txomon'
dependencies = []
files = []
hgrepos = []
issue_num = 16890
keywords = []
message_count = 5.0
messages = ['179309', '179310', '179327', '179329', '179331']
nosy_count = 2.0
nosy_names = ['ezio.melotti', 'txomon']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue16890'
versions = ['Python 3.2']

[txomon]

Hi I found something like a bug, I can't get this working:

import xml.dom.minidom as minidom
document="""<a>
    <b>
        <c />
        <c />
    </b>
</a>""" 
dom = minidom.parseString(document)

dom.childNodes
dom.childNodes[0].childNodes
dom.childNodes[0].childNodes[1].childNodes

def delete_recursive(parent):
    for child in parent.childNodes:
        if child.hasChildNodes():
            delete_recursive(child)
        else:
            parent.removeChild(child)

delete_recursive(dom)

dom.childNodes
dom.childNodes[0].childNodes
dom.childNodes[0].childNodes[0].childNodes

Executes as:
>>> import xml.dom.minidom as minidom
>>> document="""<a>
...     <b>
...         <c />
...         <c />
...     </b>
... </a>""" 
>>> dom = minidom.parseString(document)
>>> 
>>> dom.childNodes
[<DOM Element: a at 0x7f5408e717d0>]
>>> dom.childNodes[0].childNodes
[<DOM Text node "'\n    '">, <DOM Element: b at 0x7f5408e71f50>, <DOM Text node "'\n'">]
>>> dom.childNodes[0].childNodes[1].childNodes
[<DOM Text node "'\n        '">, <DOM Element: c at 0x7f5408e93290>, <DOM Text node "'\n        '">, <DOM Element: c at 0x7f5408e93310>, <DOM Text node "'\n    '">]
>>> 
>>> def delete_recursive(parent):
...     for child in parent.childNodes:
...         if child.hasChildNodes():
...             delete_recursive(child)
...         else:
...             parent.removeChild(child)
... 
>>> delete_recursive(dom)
>>> 
>>> dom.childNodes
[<DOM Element: a at 0x7f5408e717d0>]
>>> dom.childNodes[0].childNodes
[<DOM Element: b at 0x7f5408e71f50>]
>>> dom.childNodes[0].childNodes[0].childNodes
[<DOM Text node "'\n        '">, <DOM Element: c at 0x7f5408e93290>, <DOM Text node "'\n        '">, <DOM Element: c at 0x7f5408e93310>, <DOM Text node "'\n    '">]

The problem here is this last line, those text nodes shouldn't be here! I have traced the problem, and seem that the for loop is not correctly executed

[ezio-melotti]

The problem is that you are mutating parent.childNodes while you are iterating on it. Iterating over a copy seems to solve the problem.

[txomon]

I know that is the problem, but that shouldn't happen! if you remove a item
from a list, that doesn't happen. That is why I tagged the error as
minidom's
El 08/01/2013 04:24, "Ezio Melotti" <report@bugs.python.org> escribió:

Ezio Melotti added the comment:

The problem is that you are mutating parent.childNodes while you are
iterating on it. Iterating over a copy seems to solve the problem.

----------
nosy: +ezio.melotti
resolution: -> invalid
stage: -> committed/rejected
status: open -> closed
type: -> behavior

---

Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue16890\>

---

[ezio-melotti]

It happens with lists too:
>>> l = list(range(10))
>>> for x in l:
...     l.remove(x)
... 
>>> l
[1, 3, 5, 7, 9]

[txomon]

Ok, sorry then.

Javier Domingo

2013/1/8 Ezio Melotti <report@bugs.python.org>

Ezio Melotti added the comment:

It happens with lists too:
>>> l = list(range(10))
>>> for x in l:
... l.remove(x)
...
>>> l
[1, 3, 5, 7, 9]

----------

---

Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue16890\>

---