Module urllib contains method proxy_bypass_environment(domain_name). This method check if domain_name should be excluded from proxying. The domain_name is checked against environment variable no_proxy or NO_PROXY. This variable contains comma separated list of domain names/domains. Domains can be specified in following variants:

 - domain.com
 - .domain.com
 - *.domain.com

Method proxy_bypass_environment support first two variants, but it doesn't support variant with asterisk at beginning of domain. The last variant is not anything unusual; e.g.: https://www.gnu.org/software/emacs/manual/html_node/url/Proxies.html