[ python-Bugs-1699853 ] locale.getlocale() output fails as setlocale() input

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Thu Apr 19 12:18:42 CEST 2007


Bugs item #1699853, was opened at 2007-04-13 12:26
Message generated for change (Comment added) made by iszegedi
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Category: Python Library
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Bernhard Reiter (ber)
Assigned to: Nobody/Anonymous (nobody)
Summary: locale.getlocale() output fails as setlocale() input 

Initial Comment:
This problem report about the locale module
consists of three closely related parts 
(this is why I have decided to put it in one report).
a) the example in the docs is wrong / missleading
b) under some locale settings python as a defect
c) a test case for the locale module, showing b)
   but useful as general start for a test module.

Details:
        a)
        Section example:
                The line
                >>> loc = locale.getlocale(locale.LC_ALL) # get current locale
                contradicts that getlocale should not be called with
                        LC_ALL, as stated in the description of getlocale.
                Suggestion is to change the example to be more useful
                as getting the locale as first action is not really useful.
                It should be "C" anyway which will lead to (None, None)
                so the value is already known. It would make more sense to

                first set the default locale to the user preferences:
import locale
locale.setlocale(locale.LC_ALL,'')
loc = locale.getlocale(locale.LC_NUMERIC)
locale.setlocale(locale.LC_NUMERIC,"C")
# convert a string here
locale.setlocale(locale.LC_NUMERIC, loc)

                _but_ this does not work, see problem b).
                What does work is:

import
locale.setlocale(locale.LC_ALL,'')
loc = locale.setlocale(locale.LC_NUMERIC)
locale.setlocale(locale.LC_NUMERIC,"C")
# convert a string here
locale.setlocale(locale.LC_NUMERIC, loc)

Note that all_loc = locale.setlocale(locale.LC_ALL) might contain
several categories (see attached test_locale.py where I needed to decode
this).
'LC_CTYPE=de_DE.UTF-8;LC_NUMERIC=en_GB.utf8;LC_TIME=de_DE.UTF-8;LC_COLLATE=de_DE.UTF-8;LC_MONETARY=de_DE.UTF-8;LC_MESSAGES=de_DE.UTF-8;LC_PAPER=de_DE.UTF-8;LC_NAME=de_DE.UTF-8;LC_ADDRESS=de_DE.UTF-8;LC_TELEPHONE=de_DE.UTF-8;LC_MEASUREMENT=de_DE.UTF-8;LC_IDENTIFICATION=de_DE.UTF-8'


        b)
                The output of getlocale cannot be used as input to
                setlocale sometimes.
                Works with
                * python2.5 und python2.4 on
                  Debian GNU/Linux Etch ppc, de_DE.utf8.

                I had failures with
                * python2.3, python2.4, python2.5
                  on Debian GNU/Linux Sarge ppc, de_DE at euro
                * Windows XP SP2
                        python-2.4.4.msi    German, see:

                >>> import locale
                >>> result = locale.setlocale(locale.LC_NUMERIC,"")
                >>> print result
                German_Germany.1252
                >>> got = locale.getlocale(locale.LC_NUMERIC)
                >>> print got
                ('de_DE', '1252')
                >>> # works
                ... locale.setlocale(locale.LC_NUMERIC, result)
                'German_Germany.1252'
                >>> # fails
                ... locale.setlocale(locale.LC_NUMERIC, got)
                Traceback (most recent call last):
                  File "<stdin>", line 2, in ?
                  File "C:\Python24\lib\locale.py", line 381, in setlocale
                    return _setlocale(category, locale)
                locale.Error: unsupported locale setting
                >>>



----------------------------------------------------------------------

Comment By: Istvan Szegedi (iszegedi)
Date: 2007-04-19 12:18

Message:
Logged In: YES 
user_id=1772412
Originator: NO

Hi Bernhard,

I absolutely agree with you and I cannot  really judge my correction,
either. It was just a quick and dirty solution to see if it would fix the
problem. In fact, there are other ways to do it as well, like  to modify
the 
encoding_alias table not to translate utf-8 string into utf (and thus to
prevent it to produce an invalid locale setting for _setlocale )

In the locale.py file I found two names mentioned:

Author:  Mark-Andre Lemburg (mal at lemburg.com) 
and Fredrick Lund  (fredrick at pythonware.com) as a modifyier

so it might be a good idea to drop them a mail and ask for their comments.
Do you want to do it or shall I? If you are willing to do it, please, keep
me in the loop.

----------------------------------------------------------------------

Comment By: Bernhard Reiter (ber)
Date: 2007-04-19 10:55

Message:
Logged In: YES 
user_id=113859
Originator: YES

Istvan,
thanks for looking into this and adding information.
I do not feel competent to judge what the solution would be,
as I do not know the design goals of getlocale().
Given the documentation the function call would only make sense
if setlocale(getlocale(LC_XYZ)) would work in all cases, especially
after the locale has been set to the user preferances with
setlocale(LC_ALL,"")
There is no simple test case that can make sure this is the case.

The workaround for current code for me is to use setlocale(LC_XYZ) only
to ask for the currently set locale and then decipher the string if the
categories have different settings. This workaround can be seen in my
proposed test_case.py. 

I believe next steps could be to get a full overview and check design and
implementation, add some testcases so that more is covered and then fix 
the implementation. We could try to find out who invented getlocale
and ask.

----------------------------------------------------------------------

Comment By: Istvan Szegedi (iszegedi)
Date: 2007-04-19 10:24

Message:
Logged In: YES 
user_id=1772412
Originator: NO

I could reproduce the problem on Fedora Core 5 with Python 2.4.3.

After tracing down the issue, I found the following:

The problem is in locate.py. There is a function called normalize defined
in the locate.py file. This function is invoked by setlocale function if
the incoming locale argument is not a string. (in your example this
condition is true because locale.getlocale function returns a tuple so got
variable is a tuple.) The normalize function is using an encoding_alias
table which results to translate the full locale into an incorrect version.
What happens in my environment is that there is an incoming value
en_us.utf-8  which is converted to en_us.utf and that is the return value
from normalize function. Then _setlocale low level function invoked in
setlocale function throws an exception when it receives en_us.utf  argument
and it is an unsupported locale setting.


This is the original code snippet in locale.py where it is converted in a
wrong way in normalize function:


    # Second try: langname (without encoding)
    code = locale_alias.get(langname, None)
    if code is not None:
        if '.' in code:
            langname, defenc = code.split('.')
        else:
            langname = code
            defenc = ''
        if encoding:
            encoding = encoding_alias.get(encoding, encoding)
        else:
            encoding = defenc
        if encoding:
            return langname + '.' + encoding
        else:
            return langname

    else:
        return localename


To get it fixed, I modified the code in locate.py as follows:


    # Second try: langname (without encoding)
    code = locale_alias.get(langname, None)
    if code is not None:
        if '.' in code:
            langname, defenc = code.split('.')
        else:
            langname = code
            defenc = ''
#        if encoding:
#            encoding = encoding_alias.get(encoding, encoding)
#        else:
#            encoding = defenc
	if encoding is None:
	     encoding = defenc
        if encoding:
            return langname + '.' + encoding
        else:
            return langname

    else:
        return localename


So the effect of encoding_table is skipped. Then your test_locale.py
returns OK.

----------------------------------------------------------------------

Comment By: Istvan Szegedi (iszegedi)
Date: 2007-04-18 12:05

Message:
Logged In: YES 
user_id=1772412
Originator: NO

I could reproduce the problem on Fedora Core 5 with Python 2.4.3.

After tracing down the issue, I found the following:

The problem is in locate.py. There is a function called normalize defined
in the locate.py file. This function is invoked by setlocale function if
the incoming locale argument is not a string. (in your example this
condition is true because locale.getlocale function returns a tuple so got
variable is a tuple.) The normalize function is using an encoding_alias
table which results to translate the full locale into an incorrect version.
What happens in my environment is that there is an incoming value
en_us.utf-8  which is converted to en_us.utf and that is the return value
from normalize function. Then _setlocale low level function invoked in
setlocale function throws an exception when it receives en_us.utf  argument
and it is an unsupported locale setting.


This is the original code snippet in locale.py where it is converted in a
wrong way in normalize function:


    # Second try: langname (without encoding)
    code = locale_alias.get(langname, None)
    if code is not None:
        if '.' in code:
            langname, defenc = code.split('.')
        else:
            langname = code
            defenc = ''
        if encoding:
            encoding = encoding_alias.get(encoding, encoding)
        else:
            encoding = defenc
        if encoding:
            return langname + '.' + encoding
        else:
            return langname

    else:
        return localename


To get it fixed, I modified the code in locate.py as follows:


    # Second try: langname (without encoding)
    code = locale_alias.get(langname, None)
    if code is not None:
        if '.' in code:
            langname, defenc = code.split('.')
        else:
            langname = code
            defenc = ''
#        if encoding:
#            encoding = encoding_alias.get(encoding, encoding)
#        else:
#            encoding = defenc
	if encoding is None:
	     encoding = defenc
        if encoding:
            return langname + '.' + encoding
        else:
            return langname

    else:
        return localename


So the effect of encoding_table is skipped. Then your test_locale.py
returns OK.

----------------------------------------------------------------------

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