Changing the “locale preferred encoding” in Python 3 in Windows

20
votes

I'm using Python 3 (recently switched from Python 2). My code usually runs on Linux but also sometimes (not often) on Windows. According to Python 3 documentation for open(), the default encoding for a text file is from locale.getpreferredencoding() if the encoding arg is not supplied. I want this default value to be utf-8 for a project of mine, no matter what OS it's running on (currently, it's always UTF-8 for Linux, but not for Windows). The project has many many calls to open() and I don't want to add encoding='utf-8' to all of them. Thus, I want to change the locale's preferred encoding in Windows, as Python 3 sees it.

I found a previous question "Changing the "locale preferred encoding"", which has an accepted answer, so I thought I was good to go. But unfortunately, neither of the suggested commands in that answer and its first comment work for me in Windows. Specifically, that accepted answer and its first comment suggest running chcp 65001 and set PYTHONIOENCODING=UTF-8, and I've tried both. Please see transcript below from my cmd window:

> py -i
Python 3.4.3 ...
>>> f = open('foo.txt', 'w')
>>> f.encoding
'cp1252'
>>> exit()

> chcp 65001
Active code page: 65001

> py -i
Python 3.4.3 ...
>>> f = open('foo.txt', 'w')
>>> f.encoding
'cp1252'
>>> exit()

> set PYTHONIOENCODING=UTF-8

> py -i
Python 3.4.3 ...
>>> f = open('foo.txt', 'w')
>>> f.encoding
'cp1252'
>>> exit()

Note that even after both suggested commands, my opened file's encoding is still cp1252 instead of the intended utf-8.

4
pythonwindowspython-3.xencodingutf-8
Maybe it is just my style but I'd prefer to write a wrapper open() function in which you specify the encoding. - x squared
Don't use chcp 65001. The Windows console does not properly support UTF-8, and it's not doing what you want anyway. locale.getpreferredencoding has nothing to do with the console codepage; it's based on the Windows locale's ANSI encoding. For example, if you call Win32 CreateFileA (ANSI) instead of CreateFileW (UTF-16), the file path string gets decoded as an ANSI string (e.g. Windows-1252). Windows does not allow UTF-8 to be used as the ANSI character set, and the C runtime also doesn't allow using UTF-8 for a locale. - Eryk Sun
@eryksun Thanks for the info, but it has too much Windows-specific jargon for me. I rarely use Windows. All I want is a way to say to either Windows 8 or to Python 3: "Dear Windows 8 / Python 3, Please be informed that all the text files on this computer should be encoded in UTF-8 without exception. Please remember this fact in the future when opening text files. Thanks." - walrus
@walrus, no such thing exists. The native string format on Windows is UTF-16, using 16-bit wchar_t strings. The Windows API only supports 8-bit encodings for the legacy ANSI API, which unfortunately does not allow UTF-8. Python's preferred encoding is simply calling GetACP to get the ANSI codepage. I sympathize with you and wish that io.TextIOWrapper defaulted to UTF-8 on all platforms (your assumption about Linux isn't always valid, either). As things stand you need a wrapper function, as previously suggested. - Eryk Sun
A bit of effort gets you to the TextIOWrapper source and therein to see that _Py_device_encoding is what uses the Windows console codepage (GetConsoleCP), but only for stdin, stdout, and stderr. Otherwise it calls getpreferredencoding, which calls _getdefaultlocale and thus GetACP. - Eryk Sun

4 Answers

14
votes

As of python3.5.1 this hack looks like this:

import _locale
_locale._getdefaultlocale = (lambda *args: ['en_US', 'utf8'])

All files opened thereafter will assume the default encoding to be utf8.

7
votes

i know its a real hacky workaround, but you could redefine the locale.getpreferredencoding() function like so:

import locale
def getpreferredencoding(do_setlocale = True):
    return "utf-8"
locale.getpreferredencoding = getpreferredencoding

if you run this early on, all files opened after (at lest in my testing on a win xp machine) open in utf-8, and as this overrides the module method this would apply to all platforms.

1
votes

The post is old but the issue is still of actuality (under Python 3.7 and Windows 10).

I've improved the solution as follows, making sure that the language/country part isn't overwritten but only the encoding, and also to make sure that it is only done under Windows:

if os.name == "nt":
    import _locale
    _locale._gdl_bak = _locale._getdefaultlocale
    _locale._getdefaultlocale = (lambda *args: (_locale._gdl_bak()[0], 'utf8'))

Hope this helps...

0
votes

Locale can be set in windows globally to UTF-8, if you so desire, as follows:

Control panel -> Clock and Region -> Region -> Administrative -> Change system locale -> Check Beta: Use Unicode UTF-8 ...

After this, and a reboot, I confirmed that locale.getpreferredencoding() returns 'cp65001' (=UTF-8) and that functions like open default to UTF-8.