Python-сообщество

from twisted.internet.threads import deferToThread
from twisted.internet.defer import DeferredSemaphore

class Browser(object):    
    def __init__(self):
        self.sem = DeferredSemaphore(1)
    
    def _fetch(self, url, data=None):
        curl =  pycurl.Curl()
        ...
        curl.perform()
        ...
        return curl

    def fetch(self, *args, **kwargs):
        return self.sem.run(self.asyncFetch, *args, **kwargs)

    def asyncFetch(self, *args, **kwargs):
        return deferToThread(self._fetch, *args, **kwargs)