App Engine中使用BlobStore的Unicode字符

Question

有没有办法用App Engine的BlobStore存储unicode数据(在Python中)？

我正在保存这样的数据

file_name = files.blobstore.create(mime_type='application/octet-stream')
with files.open(file_name, 'a') as f:
     f.write('<as><a>' + '</a><a>'.join(stringInUnicode) + '</a></as>')

但是在生产(非开发)服务器上我遇到了这个错误.它似乎是将我的Unicode转换为ASCII,我不知道为什么.

为什么要尝试转换回ASCII？我可以避免这个吗？

    Traceback (most recent call last):
 File "/base/data/home/apps/myapp/1.349473606437967000/myfile.py", line 137, in get
   f.write('<as><a>' + '</a><a>'.join(stringInUnicode) + '</a></as>')
 File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file.py", line 364, in write
   self._make_rpc_call_with_retry('Append', request, response)
 File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file.py", line 472, in _make_rpc_call_with_retry
   _make_call(method, request, response)
 File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file.py", line 226, in _make_call
   rpc.make_call(method, request, response)
 File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_stub_map.py", line 509, in make_call
   self.__rpc.MakeCall(self.__service, method, request, response)
 File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_rpc.py", line 115, in MakeCall
   self._MakeCallImpl()
 File "/base/python_runtime/python_lib/versions/1/google/appengine/runtime/apiproxy.py", line 161, in _MakeCallImpl
   self.request.Output(e)
 File "/base/python_runtime/python_lib/versions/1/google/net/proto/ProtocolBuffer.py", line 204, in Output
   self.OutputUnchecked(e)
 File "/base/python_runtime/python_lib/versions/1/google/appengine/api/files/file_service_pb.py", line 2390, in OutputUnchecked
   out.putPrefixedString(self.data_)
 File "/base/python_runtime/python_lib/versions/1/google/net/proto/ProtocolBuffer.py", line 432, in putPrefixedString
   v = str(v)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 313: ordinal not in range(128)

Answer 1

BLOB存储包含二进制数据:字节,而不是字符.因此,您将不得不进行某种编码步骤.utf-8看起来像任何编码一样好.

f.write('<as><a>' + '</a><a>'.join(stringInUnicode) + '</a></as>')

如果在一个项目这会出问题stringInUnicode包含<,&或]]>序列.您需要进行一些转义(使用适当的XML库来序列化数据,或手动):

with files.open(file_name, 'a') as f:
    f.write('<as>')
    for line in stringInUnicode:
        line= line.replace(u'&', u'&amp;').replace(u'<', u'&lt;').replace(u'>', u'&gt;');
        f.write('<a>%s</a>' % line.encode('utf-8'))
    f.write('</as>')

(如果字符串包含控制字符,这仍然是格式不正确的XML,但是你没有那么多可以做到这一点.如果你需要在XML中存储任意二进制文件,你需要一些特殊的编码,如base- 64位在上面.)