import requests
s = requests.Session()
s.trust_env = False
This will prevent requests getting any information from its environment: specifically, it‘ll disable environment searches for proxies and for certificate bundles.
参考：
Proxy bypass detection could add delay of ~4.5 seconds to each request
requests.session之set trust_env to disable environment searches for proxies
原文：http://www.cnblogs.com/BigFishFly/p/6622831.html