1 files changed, 53 insertions, 0 deletions
diff --git a/searx/utils.py b/searx/utils.py
index 55a386bd5..ad69816ce 100644
--- a/searx/utils.py
+++ b/searx/utils.py
@@ -8,6 +8,7 @@ from os.path import splitext, join
 from random import choice
 from html.parser import HTMLParser
 from urllib.parse import urljoin, urlparse
+from collections.abc import Mapping
 
 from lxml import html
 from lxml.etree import ElementBase, XPath, XPathError, XPathSyntaxError, _ElementStringResult, _ElementUnicodeResult
@@ -500,6 +501,58 @@ def get_engine_from_settings(name):
     return {}
 
 
+NOT_EXISTS = object()
+"""Singleton used by :py:obj:`get_value` if a key does not exists."""
+
+
+def get_value(dictionary, *keys, default=NOT_EXISTS):
+    """Return the value from a *deep* mapping type (e.g. the ``settings`` object
+    from yaml).  If the path to the *key* does not exists a :py:obj:`NOT_EXISTS`
+    is returned (non ``KeyError`` exception is raised).
+
+    .. code: python
+
+       >>> from searx import settings
+       >>> from searx.utils import get_value, NOT_EXISTS
+       >>> get_value(settings, 'checker', 'additional_tests', 'rosebud', 'result_container')
+       ['not_empty', ['one_title_contains', 'citizen kane']]
+
+       >>> get_value(settings, 'search', 'xxx') is NOT_EXISTS
+       True
+       >>> get_value(settings, 'search', 'formats')
+       ['html', 'csv', 'json', 'rss']
+
+    The list returned from the ``search.format`` key is not a mapping type, you
+    can't traverse along non-mapping types.  If you try it, you will get a
+    :py:ref:`NOT_EXISTS`:
+
+    .. code: python
+
+       >>> get_value(settings, 'search', 'format', 'csv') is NOT_EXISTS
+       True
+       >>> get_value(settings, 'search', 'formats')[1]
+       'csv'
+
+    For convenience you can replace :py:ref:`NOT_EXISTS` by a default value of
+    your choice:
+
+    .. code: python
+
+       if 'csv' in get_value(settings, 'search', 'formats', default=[]):
+           print("csv format is denied")
+
+    """
+
+    obj = dictionary
+    for k in keys:
+        if not isinstance(obj, Mapping):
+            raise TypeError("expected mapping type, got %s" % type(obj))
+        obj = obj.get(k, default)
+        if obj is default:
+            return obj
+    return obj
+
+
 def get_xpath(xpath_spec):
     """Return cached compiled XPath