re-use a single request session

This should unlock performance benefits by utilising HTTP keep-alive to
reuse one TCP connection between many requests. Quoth the docs:

[The Session object] across all requests [...] will use urllib3’s
connection pooling. So if you’re making several requests to the same
host, the underlying TCP connection will be reused, which can result in
a significant performance increase (see HTTP persistent connection).[^1]

[^1]: https://requests.readthedocs.io/en/latest/user/advanced/

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 8.1.0
+
+* Reuse the same `requests.session` between requests to increase performance through HTTP Keepalive
+
 ## 8.0.1
 
 * Some minor non-functional code reformatting.

notifications_python_client/__init__.py

@@ -7,7 +7,7 @@
 #
 # -- http://semver.org/
 
-__version__ = "8.0.1"
+__version__ = "8.1.0"
 
 from notifications_python_client.errors import (  # noqa
     REQUEST_ERROR_MESSAGE,

notifications_python_client/base.py

@@ -32,6 +32,7 @@ def __init__(self, api_key, base_url="https://api.notifications.service.gov.uk",
         self.service_id = service_id
         self.api_key = api_key
         self.timeout = timeout
+        self.request_session = requests.Session()
 
     def put(self, url, data):
         return self.request("PUT", url, data=data)
@@ -87,7 +88,7 @@ def _extended_json_encoder(self, obj):
     def _perform_request(self, method, url, kwargs):
         start_time = time.monotonic()
         try:
-            response = requests.request(method, url, **kwargs)
+            response = self.request_session.request(method, url, **kwargs)
             response.raise_for_status()
             return response
         except requests.RequestException as e: