默认编码的Python标准错误？ [英] Default encoding for python for stderr?
问题描述
我已经得到了我想要（使用bash BTW）其标准错误输出定向到/ dev / null的沉默嘈杂的Python脚本。
I've got a noisy python script that I want to silence by directing its stderr output to /dev/null (using bash BTW).
像这样：
python -u parse.py 1> /tmp/output3.txt 2> /dev/null
但很快退出prematurely。嗯。我看不到出去与标准错误，因为课程的回溯。它运行大肆，通常如果我不直接标准错误的地方。
but it quickly exits prematurely. Hmm. I can't see the traceback because of course that goes out with stderr. It runs noisily and normally if I don't direct stderr somewhere.
让我们尝试重定向到一个文件，而不是某个地方的/ dev / null，并且看看它的输出：
So let's try redirecting it to a file somewhere rather than /dev/null, and take a look at what it's outputting:
python -u parse.py 1> /tmp/output3.txt 2> /tmp/foo || tail /tmp/foo
Traceback (most recent call last):
File "parse.py", line 79, in <module>
parseit('pages-articles.xml')
File "parse.py", line 33, in parseit
print >>sys.stderr, "bad page title", page_title
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-1: ordinal not in range(128)
所以，这是正在生成标准错误包含UTF8，出于某种原因，蟒蛇拒绝当它被重定向到打印非ASCII，即使它被定向到/ dev / null的（当然Python不知道）
So, the stderr that's being generated contains utf8, and for some reason python refuses to print non-ascii when it's being redirected, even though it's being directed to /dev/null (though of course python doesn't know that).
我怎么能沉默，即使它包含UTF8 python脚本的标准错误？有没有办法做到这一点，而无需重新编写每个打印到stderr在此脚本？
How can I silence the stderr of a python script even though it contains utf8? Is there any way to do it without re-writing every print to stderr in this script?
推荐答案
您可以通过沉默它绑定到一个自定义的作家标准错误：
You can silence stderr by binding it to a custom writer:
#!/usr/bin/env python
import codecs, sys
class NullWriter:
def write(self, *args, **kwargs):
pass
if len(sys.argv) == 2:
if sys.argv[1] == '1':
sys.stderr = NullWriter()
elif sys.argv[1] == '2':
#NOTE: sys.stderr.encoding is *read-only*
# therefore the whole stderr should be replaced
# encode all output using 'utf8'
sys.stderr = codecs.getwriter('utf8')(sys.stderr)
print >>sys.stderr, u"\u20AC" # euro sign
print "ok"
例如：
$ python silence_stderr.py
Traceback (most recent call last):
File "silence_stderr.py", line 11, in <module>
print >>sys.stderr, u"\u20AC"
UnicodeEncodeError: 'ascii' codec can't encode character u'\u20ac' in position 0: ordinal not in range(128)
静音标准错误：
$ python silence_stderr.py 1
ok
恩codeD标准错误：
Encoded stderr:
$ python silence_stderr.py 2
€
ok
注意：我有在Emacs上面的输出，因此效仿它，你可以做一个终端：
NOTE: I've got the above outputs inside emacs therefore to emulate it in a terminal you could do:
$ python ... 2>out.txt
$ cat out.txt
注意：深入了解Windows控制台（后 CHCP 65001 中切换到UTF-8和TrueType字体（龙力控制台））我有奇怪的结果：
NOTE: Inside Windows console (after chcp 65001 that switch to 'utf-8' and with truetype font (Lucida Console)) I've got strange results:
C:\> python silence_stderr.py 2
Traceback (most recent call last):
File "silence_stderr.py", line 14, in <module>
print >>sys.stderr, u"\u20AC" # euro sign
File "C:\pythonxy\python\lib\codecs.py", line 304, in write
self.stream.write(data)
IOError: [Errno 13] Permission denied
如果该字体没有那么的TrueType异常不提高，但输出是错误的。
If the font is not truetype then the exception doesn't raise but the output is wrong.
Perl的工程TrueType字体：
Perl works for the truetype font:
C:\> perl -E"say qq(\x{20ac})"
Wide character in print at -e line 1.
€
重定向工作虽然：
Redirection works though:
C:\>python silence_stderr.py 2 2>tmp.log
ok
C:\>cat tmp.log
€
cat: write error: Permission denied
重新注释
codecs.getwriter 文档：
中查找codeC对于给定的
编码并返回它的StreamWriter
类或工厂函数。提出了一个
LookupError 的情况下，编码
无法找到。
Look up the codec for the given encoding and return its StreamWriter class or factory function. Raises a
LookupErrorin case the encoding cannot be found.
这是过度简化的观点：
class UTF8StreamWriter:
def __init__(self, writer):
self.writer = writer
def write(self, s):
self.writer.write(s.encode('utf-8'))
sys.stderr = UTF8StreamWriter(sys.stderr)
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