title: using a proxy for whole session in requests module
body: <p>I am using burp suite as a local proxy to see the requests made.</p>
  
  <pre><code>import requests
  p = {'http': 'http://127.0.0.1:8080', 'https': 'http://127.0.0.1:8080'}
  s = requests.Session()
  s.proxies.update(p)
  res = s.get('http://httpbin.org')
  </code></pre>
  
  <p>I want to define proxy once for whole session. Using proxy every time like:</p>
  
  <pre><code>res = s.get('http://httpbin.org', proxies=p)
  </code></pre>
  
  <p>works fine but just using  <code>s.proxies.update(p)</code> doesn't work. Any thoughts? I have seen <a href="https://stackoverflow.com/a/30839005/7653529">this question</a> but no help.</p>