Fixed #30310 -- Added support for looking up HttpHeaders.headers using underscores.

django/http/request.py

@@ -369,6 +369,10 @@ class HttpHeaders(CaseInsensitiveMapping):
                 headers[name] = value
         super().__init__(headers)
 
+    def __getitem__(self, key):
+        """Allow header lookup using underscores in place of hyphens."""
+        return super().__getitem__(key.replace('_', '-'))
+
     @classmethod
     def parse_header_name(cls, header):
         if header.startswith(cls.HTTP_PREFIX):

docs/ref/request-response.txt

@@ -199,6 +199,15 @@ All attributes should be considered read-only, unless stated otherwise.
         >>> request.headers.get('user-agent')
         Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6)
 
+    For use in, for example, Django templates, headers can also be looked up
+    using underscores in place of hyphens::
+
+        {{ request.headers.user_agent }}
+
+    .. versionchanged:: 3.0
+
+        Support for look ups using underscores was added.
+
 .. attribute:: HttpRequest.resolver_match
 
     An instance of :class:`~django.urls.ResolverMatch` representing the

docs/releases/3.0.txt

@@ -217,6 +217,9 @@ Requests and Responses
 * Allowed :class:`~django.http.HttpResponse` to be initialized with
   :class:`memoryview` content.
 
+* For use in, for example, Django templates, :attr:`.HttpRequest.headers` now
+  allows look ups using underscores (e.g. ``user_agent``) in place of hyphens.
+
 Serialization
 ~~~~~~~~~~~~~
 

tests/requests/tests.py

@@ -896,6 +896,7 @@ class RequestHeadersTests(SimpleTestCase):
         request = WSGIRequest(self.ENVIRON)
         self.assertEqual(request.headers['User-Agent'], 'python-requests/1.2.0')
         self.assertEqual(request.headers['user-agent'], 'python-requests/1.2.0')
+        self.assertEqual(request.headers['user_agent'], 'python-requests/1.2.0')
         self.assertEqual(request.headers['Content-Type'], 'text/html')
         self.assertEqual(request.headers['Content-Length'], '100')