BatchHttpRequest：如何从批处理中的所有请求中收集结果？

Question

I am using BatchHttpRequest ( https://cloud.google.com/storage/docs/json_api/v1/how-tos/batch ) to collect results from multiple Http requests:

for user in all_users_in_domain:
    gmail_service = build_gmail_service_for_user(user.google_user_id)
    batch.add(gmail_service.service.users().messages().list(userId='me', q=search_query), callback=get_email_list, request_id=user_id)
batch.execute()

and then I'd like to process these aggregated results using my own logic inside the callback function get_email_list

def get_email_list(request_id, response, exception):
    message_list += response['messages']

How can I collect the array message_lists across all callbacks so I run my algorithm over all results returned in the batch of requests?

Answer 1

There are a few ways to do this, such as including your code in a class and appending to a class property (eg self.message_list).

Or you can place the callback function inside another function:

def some_outer_function():
  some_outer_function.message_list = ''

  def get_email_list(request_id, response, exception):
      some_outer_function.message_list += response['messages']

  for user in all_users_in_domain:
      gmail_service = build_gmail_service_for_user(user.google_user_id)
      batch.add(gmail_service.service.users().messages().list(userId='me', q=search_query), callback=get_email_list, request_id=user_id)
  batch.execute()

Note that you have to qualify "message_list" with the outer function name. If you simply refer to "message_list" you will be assigning to a variable that is local to "get_email_list".

You can also just use a global module variable, but I'm not a big fan of that. The class method would be my favorite option.