Question

如果我在“魔术行”中指定字符编码（由PEP 263建议）或者像

那样指定pyb模块的shebang

# -*- coding: utf-8 -*-

我可以从该模块中检索此编码吗？

（使用Python 2.7.9在Windows 7 x64上工作）

我尝试（没有成功）检索默认编码或shebang

# -*- coding: utf-8 -*-

import sys
from shebang import shebang

print "sys.getdefaultencoding():", sys.getdefaultencoding()
print "shebang:", shebang( __file__.rstrip("oc"))

将产生：

sys.getdefaultencoding（）：ascii

shebang：无

（iso-8859-1相同）

Answer 1

我在Python 2中借用了Python 3 tokenize.detect_encoding() function，调整了一点以符合Python 2的期望。我已经更改了函数签名以接受文件名并删除了包含到目前为止读取的行;你不需要那些用于你的用例：

import re
from codecs import lookup, BOM_UTF8

cookie_re = re.compile(r'^[ \t\f]*#.*?coding[:=][ \t]*([-\w.]+)')
blank_re = re.compile(br'^[ \t\f]*(?:[#\r\n]|$)')

def _get_normal_name(orig_enc):
    """Imitates get_normal_name in tokenizer.c."""
    # Only care about the first 12 characters.
    enc = orig_enc[:12].lower().replace("_", "-")
    if enc == "utf-8" or enc.startswith("utf-8-"):
        return "utf-8"
    if enc in ("latin-1", "iso-8859-1", "iso-latin-1") or \
       enc.startswith(("latin-1-", "iso-8859-1-", "iso-latin-1-")):
        return "iso-8859-1"
    return orig_enc

def detect_encoding(filename):
    bom_found = False
    encoding = None
    default = 'ascii'

    def find_cookie(line):
        match = cookie_re.match(line)
        if not match:
            return None
        encoding = _get_normal_name(match.group(1))
        try:
            codec = lookup(encoding)
        except LookupError:
            # This behaviour mimics the Python interpreter
            raise SyntaxError(
                "unknown encoding for {!r}: {}".format(
                    filename, encoding))

        if bom_found:
            if encoding != 'utf-8':
                # This behaviour mimics the Python interpreter
                raise SyntaxError(
                    'encoding problem for {!r}: utf-8'.format(filename))
            encoding += '-sig'
        return encoding

    with open(filename, 'rb') as fileobj:        
        first = next(fileobj, '')
        if first.startswith(BOM_UTF8):
            bom_found = True
            first = first[3:]
            default = 'utf-8-sig'
        if not first:
            return default

        encoding = find_cookie(first)
        if encoding:
            return encoding
        if not blank_re.match(first):
            return default

        second = next(fileobj, '')

    if not second:
        return default    
    return find_cookie(second) or default

与原始函数一样，上述函数从源文件读取两行 max ，如果cookie中的编码无效或不是UTF，则会引发SyntaxError异常8，同时存在UTF-8 BOM。

演示：

>>> import tempfile
>>> def test(contents):
...     with tempfile.NamedTemporaryFile() as f:
...         f.write(contents)
...         f.flush()
...         return detect_encoding(f.name)
...
>>> test('# -*- coding: utf-8 -*-\n')
'utf-8'
>>> test('#!/bin/env python\n# -*- coding: latin-1 -*-\n')
'iso-8859-1'
>>> test('import this\n')
'ascii'
>>> import codecs
>>> test(codecs.BOM_UTF8 + 'import this\n')
'utf-8-sig'
>>> test(codecs.BOM_UTF8 + '# encoding: latin-1\n')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in test
  File "<string>", line 37, in detect_encoding
  File "<string>", line 24, in find_cookie
SyntaxError: encoding problem for '/var/folders/w0/nl1bwj6163j2pvxswf84xcsjh2pc5g/T/tmpxsqH8L': utf-8
>>> test('# encoding: foobarbaz\n')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in test
  File "<string>", line 37, in detect_encoding
  File "<string>", line 18, in find_cookie
SyntaxError: unknown encoding for '/var/folders/w0/nl1bwj6163j2pvxswf84xcsjh2pc5g/T/tmpHiHdG3': foobarbaz

得到magic line / shebang中指定的编码（来自模块内）

1 个答案: