Get a requests session with proxy and appropriate user agent

proxy.py

import requests
from requests.adapters import HTTPAdapter

PROXIES = {
    'http': 'http://proxy.example.com:3128',
    'https': 'https://proxy.example.com:3128'
}


class ProxyUAAdapter(HTTPAdapter):
    def proxy_headers(self, proxy):
        headers = super(ProxyUAAdapter, self).proxy_headers(proxy)
        headers['User-Agent'] = 'Python'
        return headers


def get_requests_session(proxies=None):
    s = requests.Session()
    s.mount('http://', ProxyUAAdapter())
    s.mount('https://', ProxyUAAdapter())

    if proxies is None:
        proxies = PROXIES
    s.proxies.update(proxies)

    return s