From abfa1beade76b42782a9790250febce0ab6117d7 Mon Sep 17 00:00:00 2001
From: Arthur Darcet <arthur+git@darcet.fr>
Date: Mon, 7 Nov 2016 15:30:16 +0100
Subject: [PATCH] allow starting variables with an underscore

Mongo ids are useful as a named resource in a route, but they are usually named `_id` and are excluded by the current regex
---
 aiohttp/web_urldispatcher.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/aiohttp/web_urldispatcher.py b/aiohttp/web_urldispatcher.py
index a701156707a..713d58aecdd 100644
--- a/aiohttp/web_urldispatcher.py
+++ b/aiohttp/web_urldispatcher.py
@@ -694,12 +694,12 @@ def __contains__(self, route):
 
 class UrlDispatcher(AbstractRouter, collections.abc.Mapping):
 
-    DYN = re.compile(r'\{(?P<var>[a-zA-Z][_a-zA-Z0-9]*)\}')
+    DYN = re.compile(r'\{(?P<var>[_a-zA-Z][_a-zA-Z0-9]*)\}')
     DYN_WITH_RE = re.compile(
-        r'\{(?P<var>[a-zA-Z][_a-zA-Z0-9]*):(?P<re>.+)\}')
+        r'\{(?P<var>[_a-zA-Z][_a-zA-Z0-9]*):(?P<re>.+)\}')
     GOOD = r'[^{}/]+'
     ROUTE_RE = re.compile(r'(\{[_a-zA-Z][^{}]*(?:\{[^{}]*\}[^{}]*)*\})')
-    NAME_SPLIT_RE = re.compile('[.:-]')
+    NAME_SPLIT_RE = re.compile(r'[.:-]')
 
     def __init__(self, app):
         super().__init__()