New submission from STINNER Victor <victor.stin...@haypocalc.com>:
The following code fails with an AssertionError('###\ufeffdef'):
import codecs
_open = codecs.open
#_open = open
filename = "test"
with _open(filename, 'w', encoding='utf_16') as f:
f.write('abc')
pos = f.tell()
with _open(filename, 'w', encoding='utf_16') as f:
f.seek(pos)
f.write('def')
f.seek(0)
f.write('###')
with _open(filename, 'r', encoding='utf_16') as f:
content = f.read()
assert content == '###def', ascii(content)
It is a bug in StreamWriter.seek(): it should update the encoder state to not
write a new BOM. It has to be fixed in the StreamWriter class of each stateful
codec, or a stateful StreamWriter class should be implemented in the codecs
module.
Python supports the following stateful codecs:
* cp932
* cp949
* cp950
* euc_jis_2004
* euc_jisx2003
* euc_jp
* euc_kr
* gb18030
* gbk
* hz
* iso2022_jp
* iso2022_jp_1
* iso2022_jp_2
* iso2022_jp_2004
* iso2022_jp_3
* iso2022_jp_ext
* iso2022_kr
* shift_jis
* shift_jis_2004
* shift_jisx0213
* utf_8_sig
* utf_16
* utf_32
This bug has already been fixed in TextIOWrapper: issue #5006.
----------
messages: 139969
nosy: haypo
priority: normal
severity: normal
status: open
title: codecs: StreamWriter issue with stateful codecs after a seek
versions: Python 2.7, Python 3.2, Python 3.3
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue12512>
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