xml.etree.ElementTree.tostringlist does not conform to its documentation

[einarfd]

BPO	16082
Nosy	@ezio-melotti, @serhiy-storchaka

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

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GitHub fields:

assignee = None
closed_at = <Date 2012-10-09.14:19:21.537>
created_at = <Date 2012-09-28.10:51:26.664>
labels = ['expert-XML', 'type-bug', 'docs']
title = 'xml.etree.ElementTree.tostringlist does not conform to its documentation'
updated_at = <Date 2012-10-09.14:19:21.535>
user = 'https://bugs.python.org/einarfd'

bugs.python.org fields:

activity = <Date 2012-10-09.14:19:21.535>
actor = 'python-dev'
assignee = 'docs@python'
closed = True
closed_date = <Date 2012-10-09.14:19:21.537>
closer = 'python-dev'
components = ['Documentation', 'XML']
creation = <Date 2012-09-28.10:51:26.664>
creator = 'einarfd'
dependencies = []
files = []
hgrepos = []
issue_num = 16082
keywords = []
message_count = 5.0
messages = ['171434', '171445', '172299', '172482', '172483']
nosy_count = 6.0
nosy_names = ['ezio.melotti', 'eli.bendersky', 'docs@python', 'python-dev', 'serhiy.storchaka', 'einarfd']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue16082'
versions = ['Python 3.2', 'Python 3.3']

[einarfd]

The tostringlist documentation says "Returns a list of (optionally) encoded strings containing the XML data. It does not guarantee any specific sequence, except that "".join(tostringlist(element)) == tostring(element).".
But in reality it is possible to get tostringlist to return a string and not a list.
The following code will demonstrates problem, by failing with a TypeError:

from xml.etree.ElementTree import Element, tostringlist, tostring

element = Element("foo")
print ("".join(tostringlist(element)) == tostring(element))

[serhiy-storchaka]

Bug in the documentation, but not in the implementation.

See also bpo-8047 and bpo-1767933 (changeset 63845:57e631f088d7).

[elibendersky]

Thanks for the report. I'll take a look.

Patches always welcome :)

[elibendersky]

Einar, TypeError is raised because tostring/tostringlist return bytes with the default encoding, and you can't join bytes on "" (which is unicode).

[python-dev]

New changeset ff925e135e60 by Eli Bendersky in branch '3.3':
Issue bpo-16082: clarify the documentation of tostring[list] saying that it may generate a bytestring, depending on the given encoding.
http://hg.python.org/cpython/rev/ff925e135e60

New changeset 6e407fcf7380 by Eli Bendersky in branch 'default':
Merge 3.3
http://hg.python.org/cpython/rev/6e407fcf7380