Windows cmd编码更改导致Python崩溃

Question

首先，我将Windows CMD编码改为utf-8并运行Python解释器：

chcp 65001
python

然后我试着在里面打印一个unicode标记，当我这样做时，Python以一种特殊的方式崩溃（我只是在同一个窗口中得到一个cmd提示）。

>>> import sys
>>> print u'ëèæîð'.encode(sys.stdin.encoding)

有什么办法可以解释为什么会发生这种事以及如何让它起作用吗？

UPD：sys.stdin.encoding返回'cp65001'

UPD2：我刚刚想到，这个问题可能与utf-8使用multi-byte character set这一事实有关（kcwu对此提出了很好的观点）。我试着用“windows-1250”运行整个示例，得到了“eaî？”。Windows-1250使用单个字符集，因此它适用于它理解的那些字符。但是我仍然不知道如何让utf-8在这里工作。

UPD3：哦，我发现它是一个known Python bug。我猜Python会将cmd编码复制为'cp65001到sys.stdin.encoding，并尝试将其应用于所有输入。因为它无法理解“cp65001”，所以在任何包含非ascii字符的输入上都会崩溃。

Answer 1

设置pythonionecoding系统变量：

> chcp 65001
> set PYTHONIOENCODING=utf-8
> python example.py
Encoding is utf-8

example.py的来源很简单：

import sys
print "Encoding is", sys.stdin.encoding

Answer 2

您想让Python编码为UTF-8吗？

>>>print u'ëèæîð'.encode('utf-8')
ëèæîð

Python不会将cp65001识别为UTF-8。

Answer 3

下面是如何在不更改encodings\aliases.py的情况下将cp65001别名设为UTF-8：

import codecs
codecs.register(lambda name: codecs.lookup('utf-8') if name == 'cp65001' else None)

（嗯，不要在意cp65001在http://bugs.python.org/issue6058#msg97731与UTF-8不一样的愚蠢。即使微软的编解码器有一些小错误，它的目的也是一样的。）

这里有一些代码（为Tahoe LAFS，Tahoe LAFS.org编写）可以使控制台输出工作，而不必考虑chcp代码页的，还可以读取Unicode命令行参数。这个解决方案背后的想法归功于Michael Kaplan。如果stdout或stderr被重定向，它将输出UTF-8。如果需要字节顺序标记，则需要显式地编写它。

[编辑：此版本使用WriteConsoleW而不是MSVC运行库中的_O_U8TEXT标志，这是错误的。WriteConsoleW相对于MS文档来说也是错误的，但不是这样。]

import sys
if sys.platform == "win32":
    import codecs
    from ctypes import WINFUNCTYPE, windll, POINTER, byref, c_int
    from ctypes.wintypes import BOOL, HANDLE, DWORD, LPWSTR, LPCWSTR, LPVOID

    original_stderr = sys.stderr

    # If any exception occurs in this code, we'll probably try to print it on stderr,
    # which makes for frustrating debugging if stderr is directed to our wrapper.
    # So be paranoid about catching errors and reporting them to original_stderr,
    # so that we can at least see them.
    def _complain(message):
        print >>original_stderr, message if isinstance(message, str) else repr(message)

    # Work around <http://bugs.python.org/issue6058>.
    codecs.register(lambda name: codecs.lookup('utf-8') if name == 'cp65001' else None)

    # Make Unicode console output work independently of the current code page.
    # This also fixes <http://bugs.python.org/issue1602>.
    # Credit to Michael Kaplan <http://www.siao2.com/2010/04/07/9989346.aspx>
    # and TZOmegaTZIOY
    # <http://stackoverflow.com/questions/878972/windows-cmd-encoding-change-causes-python-crash/1432462#1432462>.
    try:
        # <http://msdn.microsoft.com/en-us/library/ms683231(VS.85).aspx>
        # HANDLE WINAPI GetStdHandle(DWORD nStdHandle);
        # returns INVALID_HANDLE_VALUE, NULL, or a valid handle
        #
        # <http://msdn.microsoft.com/en-us/library/aa364960(VS.85).aspx>
        # DWORD WINAPI GetFileType(DWORD hFile);
        #
        # <http://msdn.microsoft.com/en-us/library/ms683167(VS.85).aspx>
        # BOOL WINAPI GetConsoleMode(HANDLE hConsole, LPDWORD lpMode);

        GetStdHandle = WINFUNCTYPE(HANDLE, DWORD)(("GetStdHandle", windll.kernel32))
        STD_OUTPUT_HANDLE = DWORD(-11)
        STD_ERROR_HANDLE = DWORD(-12)
        GetFileType = WINFUNCTYPE(DWORD, DWORD)(("GetFileType", windll.kernel32))
        FILE_TYPE_CHAR = 0x0002
        FILE_TYPE_REMOTE = 0x8000
        GetConsoleMode = WINFUNCTYPE(BOOL, HANDLE, POINTER(DWORD))(("GetConsoleMode", windll.kernel32))
        INVALID_HANDLE_VALUE = DWORD(-1).value

        def not_a_console(handle):
            if handle == INVALID_HANDLE_VALUE or handle is None:
                return True
            return ((GetFileType(handle) & ~FILE_TYPE_REMOTE) != FILE_TYPE_CHAR
                    or GetConsoleMode(handle, byref(DWORD())) == 0)

        old_stdout_fileno = None
        old_stderr_fileno = None
        if hasattr(sys.stdout, 'fileno'):
            old_stdout_fileno = sys.stdout.fileno()
        if hasattr(sys.stderr, 'fileno'):
            old_stderr_fileno = sys.stderr.fileno()

        STDOUT_FILENO = 1
        STDERR_FILENO = 2
        real_stdout = (old_stdout_fileno == STDOUT_FILENO)
        real_stderr = (old_stderr_fileno == STDERR_FILENO)

        if real_stdout:
            hStdout = GetStdHandle(STD_OUTPUT_HANDLE)
            if not_a_console(hStdout):
                real_stdout = False

        if real_stderr:
            hStderr = GetStdHandle(STD_ERROR_HANDLE)
            if not_a_console(hStderr):
                real_stderr = False

        if real_stdout or real_stderr:
            # BOOL WINAPI WriteConsoleW(HANDLE hOutput, LPWSTR lpBuffer, DWORD nChars,
            #                           LPDWORD lpCharsWritten, LPVOID lpReserved);

            WriteConsoleW = WINFUNCTYPE(BOOL, HANDLE, LPWSTR, DWORD, POINTER(DWORD), LPVOID)(("WriteConsoleW", windll.kernel32))

            class UnicodeOutput:
                def __init__(self, hConsole, stream, fileno, name):
                    self._hConsole = hConsole
                    self._stream = stream
                    self._fileno = fileno
                    self.closed = False
                    self.softspace = False
                    self.mode = 'w'
                    self.encoding = 'utf-8'
                    self.name = name
                    self.flush()

                def isatty(self):
                    return False

                def close(self):
                    # don't really close the handle, that would only cause problems
                    self.closed = True

                def fileno(self):
                    return self._fileno

                def flush(self):
                    if self._hConsole is None:
                        try:
                            self._stream.flush()
                        except Exception as e:
                            _complain("%s.flush: %r from %r" % (self.name, e, self._stream))
                            raise

                def write(self, text):
                    try:
                        if self._hConsole is None:
                            if isinstance(text, unicode):
                                text = text.encode('utf-8')
                            self._stream.write(text)
                        else:
                            if not isinstance(text, unicode):
                                text = str(text).decode('utf-8')
                            remaining = len(text)
                            while remaining:
                                n = DWORD(0)
                                # There is a shorter-than-documented limitation on the
                                # length of the string passed to WriteConsoleW (see
                                # <http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1232>.
                                retval = WriteConsoleW(self._hConsole, text, min(remaining, 10000), byref(n), None)
                                if retval == 0 or n.value == 0:
                                    raise IOError("WriteConsoleW returned %r, n.value = %r" % (retval, n.value))
                                remaining -= n.value
                                if not remaining:
                                    break
                                text = text[n.value:]
                    except Exception as e:
                        _complain("%s.write: %r" % (self.name, e))
                        raise

                def writelines(self, lines):
                    try:
                        for line in lines:
                            self.write(line)
                    except Exception as e:
                        _complain("%s.writelines: %r" % (self.name, e))
                        raise

            if real_stdout:
                sys.stdout = UnicodeOutput(hStdout, None, STDOUT_FILENO, '<Unicode console stdout>')
            else:
                sys.stdout = UnicodeOutput(None, sys.stdout, old_stdout_fileno, '<Unicode redirected stdout>')

            if real_stderr:
                sys.stderr = UnicodeOutput(hStderr, None, STDERR_FILENO, '<Unicode console stderr>')
            else:
                sys.stderr = UnicodeOutput(None, sys.stderr, old_stderr_fileno, '<Unicode redirected stderr>')
    except Exception as e:
        _complain("exception %r while fixing up sys.stdout and sys.stderr" % (e,))


    # While we're at it, let's unmangle the command-line arguments:

    # This works around <http://bugs.python.org/issue2128>.
    GetCommandLineW = WINFUNCTYPE(LPWSTR)(("GetCommandLineW", windll.kernel32))
    CommandLineToArgvW = WINFUNCTYPE(POINTER(LPWSTR), LPCWSTR, POINTER(c_int))(("CommandLineToArgvW", windll.shell32))

    argc = c_int(0)
    argv_unicode = CommandLineToArgvW(GetCommandLineW(), byref(argc))

    argv = [argv_unicode[i].encode('utf-8') for i in xrange(0, argc.value)]

    if not hasattr(sys, 'frozen'):
        # If this is an executable produced by py2exe or bbfreeze, then it will
        # have been invoked directly. Otherwise, unicode_argv[0] is the Python
        # interpreter, so skip that.
        argv = argv[1:]

        # Also skip option arguments to the Python interpreter.
        while len(argv) > 0:
            arg = argv[0]
            if not arg.startswith(u"-") or arg == u"-":
                break
            argv = argv[1:]
            if arg == u'-m':
                # sys.argv[0] should really be the absolute path of the module source,
                # but never mind
                break
            if arg == u'-c':
                argv[0] = u'-c'
                break

    # if you like:
    sys.argv = argv

最后，它是有可能允许使用DejaVu s an s Mono，我同意这是一个很好的字体，作为控制台。

您可以在'Necessary criteria for fonts to be available in a command window' Microsoft KB中找到有关字体要求以及如何为windows控制台添加新字体的信息

但基本上，在Vista（可能也是Win7）上：

• 在HKEY_LOCAL_MACHINE_SOFTWARE\Microsoft\Windows NT\CurrentVersion\Console\TrueTypeFont下，将"0"设置为"DejaVu Sans Mono"
• 对于HKEY_CURRENT_USER\Console下的每个子键，将"FaceName"设置为"DejaVu Sans Mono"。

在XP上，检查线程'Changing Command Prompt fonts?' in LockerGnome forums。