“上关闭的文件I/O操作”

Question

我继承下面的Django视图代码，使用由另一个web服务来服务的输出数据的下载版本：

def index(request): 
    # ... (snip) ... 
    data = base64.decodestring(request.POST['data']) 
    filename = request.POST['filename'] 

    wrapper = FileWrapper(StringIO(data)) 

    response = HttpResponse(wrapper, content_type=guess_type(str(filename))[0]) 

    response['Content-Length'] = len(data) 
    response['Content-Disposition'] = "attachment; filename=" + filename 

    return response 

函数本身 - 写入反对Django 1.0 - 升级到1.5后仍然正常工作。不幸的是，覆盖这一观点现在测试失败：

def testDownload(self): 
     self.client.login(username='test', password='test') 

     real = 'abc' * 100 
     data = base64.encodestring(real) 
     response = self.client.post("/api/v1/download/", {'data': data, 'filename': 'out.jpg'}) 

     self.assertEqual(real, response.content) 
     self.assertEqual(response['Content-Disposition'], 'attachment; filename=out.jpg') 

和错误：

Traceback (most recent call last): 
    File "/home/fred/.secret_projects/final/gerbils/tests/amf.py", line 548, in testDownload 
    self.assertEqual(real, response.content) 
    File "/home/fred/.virtualenvs/cunning_plot/lib/python2.7/site-packages/django/http/response.py", line 282, in content 
    self._consume_content() 
    File "/home/carl/.virtualenvs/cunning_plot/lib/python2.7/site-packages/django/http/response.py", line 278, in _consume_content 
    self.content = b''.join(self.make_bytes(e) for e in self._container) 
    File "/home/carl/.virtualenvs/cunning_plot/lib/python2.7/site-packages/django/http/response.py", line 278, in <genexpr> 
    self.content = b''.join(self.make_bytes(e) for e in self._container) 
    File "/usr/lib64/python2.7/wsgiref/util.py", line 30, in next 
    data = self.filelike.read(self.blksize) 
    File "/usr/lib64/python2.7/StringIO.py", line 127, in read 
    _complain_ifclosed(self.closed) 
    File "/usr/lib64/python2.7/StringIO.py", line 40, in _complain_ifclosed 
    raise ValueError, "I/O operation on closed file" 
ValueError: I/O operation on closed file 

所以..任何想法？我无法看到testDownload()或index()中的任何内容，在需要阅读之前必须“关闭”StringIO。如果有什么事情，它不会影响非测试情况吗？

非常困惑。帮助赞赏。

Answer 1

查看close被调用的一个简单方法就是将子类StringIO并在关闭函数中放置一个断点。

class CustomStringIO(StringIO): 
    def close(self): 
     import pdb; pdb.set_trace() 
     super(CustomStringIO, self).close() 

堆栈这是

-> response = self.client.post("/test/", {'data': data, 'filename': 'out.jpg'}) 
    ...\venv\lib\site-packages\django\test\client.py(463)post() 
-> response = super(Client, self).post(path, data=data, content_type=content_type, **extra) 
    ...\venv\lib\site-packages\django\test\client.py(297)post() 
-> return self.request(**r) 
    ...\venv\lib\site-packages\django\test\client.py(406)request() 
-> response = self.handler(environ) 
    ...\venv\lib\site-packages\django\test\client.py(119)__call__() 
-> response.close()     # will fire request_finished 
    ...\venv\lib\site-packages\django\http\response.py(233)close() 
-> closable.close() 
> \testapp\views.py(11)close() 
-> super(CustomStringIO, self).close() 

它看起来像测试客户端是封闭的反应，这反过来又调用close上FileWrapper然后调用收盘StringIO。这是在你真正到达response.content之前。

你有什么需要的原因FileWrapper？由于HttpResponse需要字符串内容，并且base64.decodestring返回二进制字符串，因此您似乎可以直接将data直接传递给HttpResponse，而不必创建StringIO和FileWrapper。