编写CSV以存储在Google Cloud Storage中

Question

背景：我正在Python /
AppEngine项目中获取数据并创建一个.tsv文件，以便可以使用d3.js创建图表。现在，我要在每次加载页面时编写CSV文件；我想将文件一次存储在Google云端存储中，然后从那里读取文件。

每次加载页面时，我当前如何编写文件！：

def get(self):  ## this gets called when loading myfile.tsv from d3.js
    datalist = MyEntity.all()
    self.response.headers['Content-Type'] = 'text/csv'
    writer = csv.writer(self.response.out, delimiter='\t')
    writer.writerow(['field1', 'field2'])
    for eachco in datalist:
        writer.writerow([eachco.variable1, eachco.variable2])

虽然效率低下，但效果很好。

使用此Google Cloud
Storage文档
，我一直在尝试使类似的工作正常进行：

def get(self):
    filename = '/bucket/myfile.tsv'
    datalist = MyEntity.all()
    bucket_name = os.environ.get('BUCKET_NAME', app_identity.get_default_gcs_bucket_name())
    write_retry_params = gcs.RetryParams(backoff_factor=1.1)
    writer = csv.writer(self.response.out, delimiter='\t')
    gcs_file = gcs.open(filename, 'w', content_type='text/csv', retry_params=write_retry_params)
    gcs_file.write(writer.writerow(['field1', 'field2']))
    for eachco in datalist:
        gcs_file.write(writer.writerow([eachco.variable1, eachco.variable2]))
    gcs_file.close()

但是我得到了：

TypeError: Expected str but got <type 'NoneType'>.

我以为csv.writer的输出将是一个字符串，所以我不确定为什么会收到TypeError。

所以我可以想到两种情况：

1. 我在将tsv写入Cloud Storage的代码中搞砸了。遍历并将TSV / CSV文件写入Cloud Storage应该很简单，对吧？
2. 我完全采用了完全错误的方法，甚至应该使用BlobStore或db.TextProperty（）来存储此.tsv数据。（文件不是那么大；绝对小于1MB）

我将不胜感激！

编辑-完整回溯

Traceback (most recent call last):
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.1/webapp2.py", line 1530, in __call__
    rv = self.router.dispatch(request, response)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.1/webapp2.py", line 1278, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.1/webapp2.py", line 1102, in __call__
    return handler.dispatch()
  File "/mydirectory/myapp/handlers.py", line 21, in dispatch
    webapp2.RequestHandler.dispatch(self)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.1/webapp2.py", line 572, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.1/webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "/mydirectory/myapp/thisapp.py", line 384, in get
    gcs_file.write(writer.writerow(['field1', 'field2']))
  File "lib/cloudstorage/storage_api.py", line 754, in write
    raise TypeError('Expected str but got %s.' % type(data))
TypeError: Expected str but got <type 'NoneType'>.

Answer 1

您仍在尝试根据响应创建作者：

writer = csv.writer(self.response.out, delimiter='\t')

您需要写入GCS文件。像这样：

    datalist = MyEntity.all()
    bucket_name = os.environ.get('BUCKET_NAME', app_identity.get_default_gcs_bucket_name())
    filename = os.path.join(bucket_name, 'myfile.tsv')
    write_retry_params = gcs.RetryParams(backoff_factor=1.1)
    gcs_file = gcs.open(filename, 'w', content_type='text/csv', retry_params=write_retry_params)
    writer = csv.writer(gcs_file, delimiter='\t')
    writer.writerow(['field1', 'field2'])
    for eachco in datalist:
        writer.writerow([eachco.variable1, eachco.variable2])
    gcs_file.close()

笔记：

• 尚未实际测试
• 我还调整了文件名以使用 bucket_name
• 如果您在get()请求中执行此操作，则可能需要检查文件是否已存在，如果存在，请使用它，否则您仍会在每次请求时生成该文件。或者，您可以将此代码移至任务或.tsv上载处理程序中。