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Hi, the following works in 2.7 but not in 3.x:
>>> import locale
>>> from decimal import *
>>> locale.setlocale(locale.LC_NUMERIC, 'fi_FI')
'fi_FI'
>>> format(Decimal('1000'), 'n')
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/usr/lib/python3.2/decimal.py", line 3632, in __format__
 spec = _parse_format_specifier(specifier, _localeconv=_localeconv)
 File "/usr/lib/python3.2/decimal.py", line 5628, in
_parse_format_specifier
 _localeconv = _locale.localeconv()
 File "/usr/lib/python3.2/locale.py", line 111, in localeconv
 d = _localeconv()
ValueError: Cannot convert byte to string

This fails in _localemodule.c: str2uni(). mbstowcs(NULL, s, 0) is
LC_CTYPE sensitive, but LC_CTYPE is UTF-8 in my terminal.
If I set LC_CTYPE and LC_NUMERIC together, things work.
This raises the question: If LC_CTYPE and LC_NUMERIC differ (and
since they are separate entities I assume they may differ), what
is the correct way to convert the separator and the decimal point?
a) call setlocale(LC_CTYPE, setlocale(LC_NUMERIC, NULL)) before
 mbstowcs. This is not really an option.
b) use some kind of _mbstowcs_l
(http://msdn.microsoft.com/en-us/library/k1f9b8cy(VS.80).aspx), which
takes a locale parameter. But I don't
find such a thing on Linux.

I'm failing to reproduce this (with py3k) on OS X:
Python 3.2a0 (py3k:76866:76867, Dec 17 2009, 09:19:26) 
[GCC 4.2.1 (Apple Inc. build 5646) (dot 1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import locale
>>> from decimal import *
>>> locale.setlocale(locale.LC_NUMERIC, 'fi_FI')
'fi_FI'
>>> format(Decimal('1000'), 'n')
'1.000'
The locale command, from the same Terminal prompt, gives me:
LANG="en_IE.UTF-8"
LC_COLLATE="en_IE.UTF-8"
LC_CTYPE="en_IE.UTF-8"
LC_MESSAGES="en_IE.UTF-8"
LC_MONETARY="en_IE.UTF-8"
LC_NUMERIC="en_IE.UTF-8"
LC_TIME="en_IE.UTF-8"
LC_ALL=
Just to be clear, is is true that you still get the same result without 
involving Decimal at all? That is, am I correct in assuming that:
>>> import locale
>>> locale.setlocale(locale.LC_NUMERIC, 'fi_FI')
'fi_FI'
>>> locale.localeconv()
also gives you that ValueError?

What are the multibyte strings that mbstowcs is failing to convert?
On my machine, the separators come out as plain ASCII '.' (for thousands) 
and ',' (for the decimal point).

I can reproduce it on a Fedora (fc6) Linux box. It's not a decimal
problem, but a plain locale problem:
>>> import locale
>>> locale.setlocale(locale.LC_NUMERIC, 'fi_FI')
'fi_FI'
>>> locale.localeconv()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/root/python/py3k/Lib/locale.py", line 111, in localeconv
 d = _localeconv()
ValueError: Cannot convert byte to string
>>> 
Here's the contents of the struct lconv as returned by localeconv():
((gdb) p *l
1ドル = {decimal_point = 0xb7b54020 ",", thousands_sep = 0xb7b54022 " ",
grouping = 0xb7b54024 "003円003円", 
 int_curr_symbol = 0x998858 "", currency_symbol = 0x998858 "",
mon_decimal_point = 0x998858 "", mon_thousands_sep = 0x998858 "", 
 mon_grouping = 0x998858 "", positive_sign = 0x998858 "", negative_sign
= 0x998858 "", int_frac_digits = 127 '177円', 
 frac_digits = 127 '177円', p_cs_precedes = 127 '177円', p_sep_by_space =
127 '177円', n_cs_precedes = 127 '177円', 
 n_sep_by_space = 127 '177円', p_sign_posn = 127 '177円', n_sign_posn =
127 '177円', int_p_cs_precedes = 127 '177円', 
 int_p_sep_by_space = 127 '177円', int_n_cs_precedes = 127 '177円',
int_n_sep_by_space = 127 '177円', int_p_sign_posn = 127 '177円', 
 int_n_sign_posn = 127 '177円'}
The problem is thousands_sep:
(gdb) p l->thousands_sep
2ドル = 0xb7b54022 " "
(gdb) p (unsigned char)l->thousands_sep[0]
3ドル = 160 ' '

Yes, it's a problem in _localemodule.c. This situation always
occurs when LC_NUMERIC is something like ISO8859-15, LC_CTYPE
is UTF-8 AND the decimal point or separator are in the range
128-255. Then mbstowcs tries to decode the character according
to LC_CTYPE and finds that the character is not valid UTF-8:
static PyObject*mbstowcs
str2uni(const char* s)
{
#ifdef HAVE_BROKEN_MBSTOWCS
 size_t needed = strlen(s);
#else
 size_t needed = mbstowcs(NULL, s, 0);
#endif
I can't see a portable way to fix this except:
block threads
set temporary LC_CTYPE
call mbstowcs
restore LC_CTYPE
unblock threads
I don't think this issue is important enough to do that. What
I do in cdecimal is raise an error "Invalid separator or
unsupported combination of LC_NUMERIC and LC_CTYPE".

Changed title (was: decimal.py: format failure with locale specifier)

I have a patch that fixes this specific issue. Probably there are similar
issues in other places, e.g. when LC_TIME and LC_CTYPE differ.
I suspect that this is related:
http://bugs.python.org/issue5905 

Could we have a patch review please. Also note that #5905 has been closed.

Is this the same as when tests with python-3.3.2 fails on me with RHEL-6?
test_locale (test.test_format.FormatTest) ... ERROR
test_non_ascii (test.test_format.FormatTest) ... test test_format failed
'\u20ac=%f' % (1.0,) =? '\u20ac=1.000000' ... yes
ok
======================================================================
ERROR: test_locale (test.test_format.FormatTest)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/matej/build/Extras/python3/Python-3.Lib/test/test_format.py", line 295, in test_locale
 localeconv = locale.localeconv()
 File "/home/matej/build/Extras/python3/Python-3.Lib/locale.py", line 111, in localeconv
 d = _localeconv()
UnicodeDecodeError: 'locale' codec can't decode byte 0xe2 in position 0: Invalid or incomplete multibyte or wide character
----------------------------------------------------------------------

Matej Cepl <report@bugs.python.org> wrote:
> Is this the same as when tests with python-3.3.2 fails on me with RHEL-6?
If LC_CTYPE is UTF-8 and LC_NUMERIC something like ISO-8859-2 then it's
the same issue.

Hmm, so with this patch
diff -up Python-3.Lib/test/test_format.py.fixFormatTest Python-3.Lib/test/test_format.py
--- Python-3.Lib/test/test_format.py.fixFormatTest 2013年10月22日 10:05:12.253426746 +0200
+++ Python-3.Lib/test/test_format.py 2013年10月22日 10:16:58.510530570 +0200
@@ -288,7 +288,7 @@ class FormatTest(unittest.TestCase):
 def test_locale(self):
 try:
 oldloc = locale.setlocale(locale.LC_ALL)
- locale.setlocale(locale.LC_ALL, '')
+ locale.setlocale(locale.LC_ALL, 'ps_AF')
 except locale.Error as err:
 self.skipTest("Cannot set locale: {}".format(err))
 try:
(or any other explicit locale, I have tried also en_IE) test doesn't fail.
Using Python-3.3.2 on RHEL-6 (kernel 2.6.32-358.23.2.el6.i686).

To #200912: now, system locale is UTF-8 all the way:
santiago:python3 (el6) $ locale
LANG=en_US.utf8
LC_CTYPE="en_US.utf8"
LC_NUMERIC=en_IE.utf8
LC_TIME=en_IE.utf8
LC_COLLATE="en_US.utf8"
LC_MONETARY=en_IE.utf8
LC_MESSAGES="en_US.utf8"
LC_PAPER=en_IE.utf8
LC_NAME="en_US.utf8"
LC_ADDRESS="en_US.utf8"
LC_TELEPHONE="en_US.utf8"
LC_MEASUREMENT=en_IE.utf8
LC_IDENTIFICATION="en_US.utf8"
LC_ALL=
santiago:python3 (el6) $

Matej Cepl <report@bugs.python.org> wrote:
> To #200912: now, system locale is UTF-8 all the way:
> santiago:python3 (el6) $ locale
> LANG=en_US.utf8
> LC_CTYPE="en_US.utf8"
> LC_NUMERIC=en_IE.utf8
> LC_TIME=en_IE.utf8
> LC_COLLATE="en_US.utf8"
> LC_MONETARY=en_IE.utf8
> LC_MESSAGES="en_US.utf8"
> LC_PAPER=en_IE.utf8
> LC_NAME="en_US.utf8"
> LC_ADDRESS="en_US.utf8"
> LC_TELEPHONE="en_US.utf8"
> LC_MEASUREMENT=en_IE.utf8
> LC_IDENTIFICATION="en_US.utf8"
> LC_ALL=
> santiago:python3 (el6) $
The test passes here with these values (Debian).
What is the output of:
 a) locale.localeconv()
 b) locale.setlocale(locale.LC_ALL, '')
 locale.localeconv()

This issue is very close to the issue #13706 which I solved with the new function PyUnicode_DecodeLocale(): see get_locale_info() in Python/formatter_unicode.c.
We might copy/paste the code, or we should maybe add a private API to get locale information: get_locale_info() => _Py_get_locale_info() and expose the LocaleInfo structure. It may be added to unicodeobject.h for example, there is already a function related to locales: _PyUnicode_InsertThousandsGrouping().

>>> import locale
>>> locale.localeconv()
{'p_cs_precedes': 127, 'n_sep_by_space': 127, 'n_sign_posn': 127, 'n_cs_precedes': 127, 'grouping': [], 'positive_sign': '', 'mon_grouping': [], 'p_sep_by_space': 127, 'mon_thousands_sep': '', 'currency_symbol': '', 'mon_decimal_point': '', 'int_curr_symbol': '', 'thousands_sep': '', 'frac_digits': 127, 'int_frac_digits': 127, 'negative_sign': '', 'decimal_point': '.', 'p_sign_posn': 127}
>>> locale.setlocale(locale.LC_ALL, '')
'LC_CTYPE=en_US.utf8;LC_NUMERIC=en_IE.utf8;LC_TIME=en_IE.utf8;LC_COLLATE=en_US.utf8;LC_MONETARY=en_IE.utf8;LC_MESSAGES=en_US.utf8;LC_PAPER=en_IE.utf8;LC_NAME=en_US.utf8;LC_ADDRESS=en_US.utf8;LC_TELEPHONE=en_US.utf8;LC_MEASUREMENT=en_IE.utf8;LC_IDENTIFICATION=en_US.utf8'
>>> locale.localeconv()
{'p_cs_precedes': 1, 'n_sep_by_space': 0, 'n_sign_posn': 1, 'n_cs_precedes': 1, 'grouping': [3, 3, 0], 'positive_sign': '', 'mon_grouping': [3, 3, 0], 'p_sep_by_space': 0, 'mon_thousands_sep': ',', 'currency_symbol': '€', 'mon_decimal_point': '.', 'int_curr_symbol': 'EUR ', 'thousands_sep': ',', 'frac_digits': 2, 'int_frac_digits': 2, 'negative_sign': '-', 'decimal_point': '.', 'p_sign_posn': 1}
>>>

Perhaps version of glibc might be interesting as well?
glibc-2.12-1.107.el6_4.5.i686

Matej Cepl <report@bugs.python.org> wrote:
> >>> import locale
> >>> locale.localeconv()
> {'p_cs_precedes': 127, 'n_sep_by_space': 127, 'n_sign_posn': 127, 'n_cs_precedes': 127, 'grouping': [], 'positive_sign': '', 'mon_grouping': [], 'p_sep_by_space': 127, 'mon_thousands_sep': '', 'currency_symbol': '', 'mon_decimal_point': '', 'int_curr_symbol': '', 'thousands_sep': '', 'frac_digits': 127, 'int_frac_digits': 127, 'negative_sign': '', 'decimal_point': '.', 'p_sign_posn': 127}
> >>> locale.setlocale(locale.LC_ALL, '')
> 'LC_CTYPE=en_US.utf8;LC_NUMERIC=en_IE.utf8;LC_TIME=en_IE.utf8;LC_COLLATE=en_US.utf8;LC_MONETARY=en_IE.utf8;LC_MESSAGES=en_US.utf8;LC_PAPER=en_IE.utf8;LC_NAME=en_US.utf8;LC_ADDRESS=en_US.utf8;LC_TELEPHONE=en_US.utf8;LC_MEASUREMENT=en_IE.utf8;LC_IDENTIFICATION=en_US.utf8'
> >>> locale.localeconv()
> {'p_cs_precedes': 1, 'n_sep_by_space': 0, 'n_sign_posn': 1, 'n_cs_precedes': 1, 'grouping': [3, 3, 0], 'positive_sign': '', 'mon_grouping': [3, 3, 0], 'p_sep_by_space': 0, 'mon_thousands_sep': ',', 'currency_symbol': '€', 'mon_decimal_point': '.', 'int_curr_symbol': 'EUR ', 'thousands_sep': ',', 'frac_digits': 2, 'int_frac_digits': 2, 'negative_sign': '-', 'decimal_point': '.', 'p_sign_posn': 1}
These look normal. I'm puzzled, because that's what is going on in the test
as well. Do you get the failure when running the test in isolation:
./python -m test test_format
If this passes, there might be some interaction with other tests.
If it doesn't pass, I would step through the test in gdb (break PyLocale_localeconv)
and see which member of struct lconv is the troublemaker.

Title: _localemodule.c: str2uni() with different LC_NUMERIC and LC_CTYPE
Oh, I just realized that the issue is a LC_NUMERIC using an encoding A with a LC_CTYPE using an encoding B. It looks like the glibc does not support this setup, at least for the fi_FI locale which has a non-ASCII thousand separator (non-breaking space: U+00A0).
Try attached inconsistent_locale_encodings.py script (it uses locale names for Fedora 19, you may have to adapt it to your OS).
Output on Fedora 19:
fi_FI numeric (ISO-8859-1) with fr_FR.utf8 ctype (UTF-8)
UnicodeDecodeError: 'locale' codec can't decode byte 0xa0 in position 0: Virheellinen tai epätäydellinen monitavumerkki tai leveä merkki
fi_FI@euro numeric (ISO-8859-15) with fr_FR.utf8 ctype (UTF-8)
UnicodeDecodeError: 'locale' codec can't decode byte 0xa0 in position 0: Virheellinen tai epätäydellinen monitavumerkki tai leveä merkki
fi_FI.iso88591 numeric (ISO-8859-1) with fr_FR.utf8 ctype (UTF-8)
UnicodeDecodeError: 'locale' codec can't decode byte 0xa0 in position 0: Virheellinen tai epätäydellinen monitavumerkki tai leveä merkki
fi_FI.iso885915@euro numeric (ISO-8859-15) with fr_FR.utf8 ctype (UTF-8)
UnicodeDecodeError: 'locale' codec can't decode byte 0xa0 in position 0: Virheellinen tai epätäydellinen monitavumerkki tai leveä merkki
fi_FI.utf8 numeric (UTF-8) with fr_FR.utf8 ctype (UTF-8)
{'grouping': [3, 3, 0], 'p_cs_precedes': 0, 'mon_thousands_sep': '\xa0', 'decimal_point': ',', 'n_sep_by_space': 1, 'n_sign_posn': 1, 'mon_decimal_point': ',', 'frac_digits': 2, 'positive_sign': '', 'mon_grouping': [3, 3, 0], 'n_cs_precedes': 0, 'thousands_sep': '\xa0', 'p_sep_by_space': 1, 'p_sign_posn': 1, 'int_frac_digits': 2, 'currency_symbol': '€', 'negative_sign': '-', 'int_curr_symbol': 'EUR '}

msg95988> Hi, the following works in 2.7 but not in 3.x: ...
Sure it works because Python 2 pass the raw byte string, it does not try to decode it. But did you try to display the result in a terminal for example?
Example with Python 2 in an UTF-8 terminal:
$ python
Python 2.7.5 (default, Oct 8 2013, 12:19:40) 
[GCC 4.8.1 20130603 (Red Hat 4.8.1-1)] on linux2
>>> import locale
>>> # set the locale encoding to UTF-8
... locale.setlocale(locale.LC_CTYPE, 'fr_FR.utf8')
'fr_FR.utf8'
>>> # set the thousand separator to U+00A0
... locale.setlocale(locale.LC_NUMERIC, 'fi_FI')
'fi_FI'
>>> locale.getlocale(locale.LC_CTYPE)
('fr_FR', 'UTF-8')
>>> locale.getlocale(locale.LC_NUMERIC)
('fi_FI', 'ISO8859-15')
>>> locale.format('%d', 123456, True)
'123\xa0456'
>>> print(locale.format('%d', 123456, True))
123�456
Mojibake! � means that b'\xA0' cannot be decoded from the locale encoding (UTF-8).
There is probably the same issue with a LC_MONETARY using a different encoding than LC_CTYPE.
> I suspect that this is related: #5905
It is unrelated: time.strftime() uses the LC_CTYPE, but the Python was using the wrong encoding. Python used the locale encoding read at startup, whereas the *current* locale encoding must be used.
This issue is specific to LC_NUMERIC with a LC_CTYPE using different encoding.
> If I set LC_CTYPE and LC_NUMERIC together, things work.
Sure, because in this case, LC_NUMERIC produces data in the same encoding than LC_CTYPE.
> call setlocale(LC_CTYPE, setlocale(LC_NUMERIC, NULL)) before
> mbstowcs. This is not really an option.
Setting a locale is process-wide and should be avoided. FYI locale.getpreferredencoding() changes temporarly the LC_CTYPE by default, it only uses the current LC_CTYPE if you pass False. open() changed temporarly LC_CTYPE because of that in Python 3.0-3.2 (see issue #11022).
The following PostgreSQL issue looks to be the same than this Python issue:
4B7E07541D0@cvs.postgresql.org">http://www.postgresql.org/message-id/20100422015552.4B7E07541D0@cvs.postgresql.org
The fix changes temporarly the LC_CTYPE encoding:
#ifdef WIN32
setlocale(LC_CTYPE, locale_monetary);
#endif
(I don't know why the code is specific to Windows.)

STINNER Victor <report@bugs.python.org> wrote:
> The following PostgreSQL issue looks to be the same than this Python issue:
> 4B7E07541D0@cvs.postgresql.org">http://www.postgresql.org/message-id/20100422015552.4B7E07541D0@cvs.postgresql.org
> 
> The fix changes temporarly the LC_CTYPE encoding:
So does my patch. :)

What I did:
1) run the build (it is a building of Fedora Rawhide python3 package on RHEL), and see it failed in this test.
2) see below
santiago:python3 (el6) $ cd Python-3.3.2/build/optimized/
santiago:optimized (el6) $ ./python -m test test_format
[1/1] test_format
1 test OK.
santiago:optimized (el6) $ 
Oh well

Victor, thanks for the comments. I also think we should set LC_CTYPE closer
to the actual call to mbstowcs(), otherwise there are many API calls in
between.
So it should happen somewhere in PyUnicode_DecodeLocaleAndSize(). Perhaps
we can create _PyUnicode_DecodeLocaleAndSize() which would take an LC_CTYPE
parameter?

Matej Cepl <report@bugs.python.org> wrote:
> santiago:optimized (el6) $ ./python -m test test_format
> [1/1] test_format
> 1 test OK.
It looks like some other test in the test suite did not restore a changed
locale. If you're motivated enough, you could try if it still happens in
3.4 and open a new issue (it's unrelated to this one).

"So it should happen somewhere in PyUnicode_DecodeLocaleAndSize(). Perhaps we can create _PyUnicode_DecodeLocaleAndSize() which would take an LC_CTYPE parameter?"
For this issue, it means that Python localeconv() will have to change the LC_CTYPE locale many time, for each monetary and each number value. I prefer your patch :-)

On 22/10/13 17:32, Stefan Krah wrote:
> It looks like some other test in the test suite did not restore a changed
> locale. If you're motivated enough, you could try if it still happens in
> 3.4 and open a new issue (it's unrelated to this one).
Very plain checkout of git and ./configure && make && make test leads to
another failed test, but not this one (issue #19353). So either we do
something wrong in all those Fedora patches, or this has been fixed
since 3.3.2.
Curiouser and curiouser.

STINNER Victor <report@bugs.python.org> wrote:
> "So it should happen somewhere in PyUnicode_DecodeLocaleAndSize(). Perhaps we can create _PyUnicode_DecodeLocaleAndSize() which would take an LC_CTYPE parameter?"
> 
> For this issue, it means that Python localeconv() will have to change the LC_CTYPE locale many time, for each monetary and each number value. I prefer your patch :-)
Windows and OS X have mbstowcs_l(), which takes a locale arg. Linux doesn't
(as far as I can see). I agree this solution is ugly, but it probably won't
have an impact on benchmarks (naively assuming that setlocale() is fast).

Here's a quick-and-dirty version of mbstowcs_l(). The difference in the
benchmark to the plain mbstowcs() is 0.82s vs 0.55s. In the context of
a Python function this is unlikely to be measurable.

@Stefan: Did you my comments on Rietveld?
http://bugs.python.org/review/7442/#ps1473 

Yes, I saw the comments. I'm still wondering if we should just write an
mbstowcs_l() function instead.
Even then, there would still be a small chance that a C extension that
creates its own thread picks up the wrong LC_CTYPE.

What is this locale_t type used for the locale parameter of mbstowcs_l()? Are you sure that it is a string? According to this patch, it looks like a structure:
http://www.winehq.org/pipermail/wine-cvs/2010-May/067264.html 

STINNER Victor <report@bugs.python.org> wrote:
> What is this locale_t type used for the locale parameter of mbstowcs_l()?
> Are you sure that it is a string? According to this patch, it looks like a structure:
> http://www.winehq.org/pipermail/wine-cvs/2010-May/067264.html
Yes, the string was mainly for benchmarking. FreeBSD seems to have thread safe
versions (xlocale.h), that take a locale_t as the extra parameter.

Well, I originally opened this issue but personally I'm not that
bothered by it any more.
Victor, do you want to keep it open?

The issue has a workaround: use LC_NUMERIC and LC_CTYPE locales which use the same encoding. To avoid issues, it's probably safer to only use UTF-8 locales, which are now available on modern Linux distro.
I don't like the idea of calling setlocale() just for this corner case, because it changes the locale for all threads. Even if Python is protected by the GIL, Python can be embedded or modules written in C may spawn threads which don't care of the GIL. Usually, if it can fail, it will fail :-)
I see that various people contributed to the issue, but it looks like the only user asking for the request is Stefan Krah. I prefer to close the issue and wait until more users ask for it before considering again the patch, or find a different way to implement the feature (support LC_NUMERIC and LC_CTYPE locales using a different encoding).
To be clear, I'm closing the issue right now.

> I prefer to close the issue and wait until more users ask for it before considering again the patch, or find a different way to implement the feature (support LC_NUMERIC and LC_CTYPE locales using a different encoding).
Here we are: https://bugs.python.org/issue31900