diff --git a/firebase/firebase.py b/firebase/firebase.py
index e62576d..aac5980 100644
--- a/firebase/firebase.py
+++ b/firebase/firebase.py
@@ -243,8 +243,7 @@ def _build_endpoint_url(self, url, name=None):
             url = url + self.URL_SEPERATOR
         if name is None:
             name = ''
-        return '%s%s%s' % (urlparse.urljoin(self.dsn, url), name,
-                           self.NAME_EXTENSION)
+        return f'{urlparse.urljoin(self.dsn, url)}{name}{self.NAME_EXTENSION}'
 
     def _authenticate(self, params, headers):
         """