bpo-40624: Add support for the XPath != operator in xml.etree (GH-22147)

Doc/library/xml.etree.elementtree.rst

@@ -455,6 +455,12 @@ Supported XPath syntax
 |                       | has the given value.  The value cannot contain       |
 |                       | quotes.                                              |
 +-----------------------+------------------------------------------------------+
+| ``[@attrib!='value']``| Selects all elements for which the given attribute   |
+|                       | does not have the given value. The value cannot      |
+|                       | contain quotes.                                      |
+|                       |                                                      |
+|                       | .. versionadded:: 3.10                               |
++-----------------------+------------------------------------------------------+
 | ``[tag]``             | Selects all elements that have a child named         |
 |                       | ``tag``.  Only immediate children are supported.     |
 +-----------------------+------------------------------------------------------+
@@ -463,10 +469,22 @@ Supported XPath syntax
 |                       |                                                      |
 |                       | .. versionadded:: 3.7                                |
 +-----------------------+------------------------------------------------------+
+| ``[.!='text']``       | Selects all elements whose complete text content,    |
+|                       | including descendants, does not equal the given      |
+|                       | ``text``.                                            |
+|                       |                                                      |
+|                       | .. versionadded:: 3.10                               |
++-----------------------+------------------------------------------------------+
 | ``[tag='text']``      | Selects all elements that have a child named         |
 |                       | ``tag`` whose complete text content, including       |
 |                       | descendants, equals the given ``text``.              |
 +-----------------------+------------------------------------------------------+
+| ``[tag!='text']``     | Selects all elements that have a child named         |
+|                       | ``tag`` whose complete text content, including       |
+|                       | descendants, does not equal the given ``text``.      |
+|                       |                                                      |
+|                       | .. versionadded:: 3.10                               |
++-----------------------+------------------------------------------------------+
 | ``[position]``        | Selects all elements that are located at the given   |
 |                       | position.  The position can be either an integer     |
 |                       | (1 is the first position), the expression ``last()`` |

Lib/test/test_xml_etree.py

@@ -2852,8 +2852,12 @@ class ElementFindTest(unittest.TestCase):
             ['tag'] * 3)
         self.assertEqual(summarize_list(e.findall('.//tag[@class="a"]')),
             ['tag'])
+        self.assertEqual(summarize_list(e.findall('.//tag[@class!="a"]')),
+            ['tag'] * 2)
         self.assertEqual(summarize_list(e.findall('.//tag[@class="b"]')),
             ['tag'] * 2)
+        self.assertEqual(summarize_list(e.findall('.//tag[@class!="b"]')),
+            ['tag'])
         self.assertEqual(summarize_list(e.findall('.//tag[@id]')),
             ['tag'])
         self.assertEqual(summarize_list(e.findall('.//section[tag]')),
@@ -2875,6 +2879,19 @@ class ElementFindTest(unittest.TestCase):
         self.assertEqual(summarize_list(e.findall(".//section[ tag = 'subtext' ]")),
             ['section'])
 
+        # Negations of above tests. They match nothing because the sole section
+        # tag has subtext.
+        self.assertEqual(summarize_list(e.findall(".//section[tag!='subtext']")),
+            [])
+        self.assertEqual(summarize_list(e.findall(".//section[tag !='subtext']")),
+            [])
+        self.assertEqual(summarize_list(e.findall(".//section[tag!= 'subtext']")),
+            [])
+        self.assertEqual(summarize_list(e.findall(".//section[tag != 'subtext']")),
+            [])
+        self.assertEqual(summarize_list(e.findall(".//section[ tag != 'subtext' ]")),
+            [])
+
         self.assertEqual(summarize_list(e.findall(".//tag[.='subtext']")),
                          ['tag'])
         self.assertEqual(summarize_list(e.findall(".//tag[. ='subtext']")),
@@ -2890,6 +2907,24 @@ class ElementFindTest(unittest.TestCase):
         self.assertEqual(summarize_list(e.findall(".//tag[.= ' subtext']")),
                          [])
 
+        # Negations of above tests.
+        #   Matches everything but the tag containing subtext
+        self.assertEqual(summarize_list(e.findall(".//tag[.!='subtext']")),
+                         ['tag'] * 3)
+        self.assertEqual(summarize_list(e.findall(".//tag[. !='subtext']")),
+                         ['tag'] * 3)
+        self.assertEqual(summarize_list(e.findall('.//tag[.!= "subtext"]')),
+                         ['tag'] * 3)
+        self.assertEqual(summarize_list(e.findall('.//tag[ . != "subtext" ]')),
+                         ['tag'] * 3)
+        self.assertEqual(summarize_list(e.findall(".//tag[. != 'subtext']")),
+                         ['tag'] * 3)
+        # Matches all tags.
+        self.assertEqual(summarize_list(e.findall(".//tag[. != 'subtext ']")),
+                         ['tag'] * 4)
+        self.assertEqual(summarize_list(e.findall(".//tag[.!= ' subtext']")),
+                         ['tag'] * 4)
+
         # duplicate section => 2x tag matches
         e[1] = e[2]
         self.assertEqual(summarize_list(e.findall(".//section[tag = 'subtext']")),

Lib/xml/etree/ElementPath.py

@@ -65,8 +65,9 @@ xpath_tokenizer_re = re.compile(
     r"//?|"
     r"\.\.|"
     r"\(\)|"
+    r"!=|"
     r"[/.*:\[\]\(\)@=])|"
-    r"((?:\{[^}]+\})?[^/\[\]\(\)@=\s]+)|"
+    r"((?:\{[^}]+\})?[^/\[\]\(\)@!=\s]+)|"
     r"\s+"
     )
 
@@ -253,15 +254,19 @@ def prepare_predicate(next, token):
                 if elem.get(key) is not None:
                     yield elem
         return select
-    if signature == "@-='":
+    if signature == "@-='" or signature == "@-!='":
-        # [@attribute='value']
+        # [@attribute='value'] or [@attribute!='value']
         key = predicate[1]
         value = predicate[-1]
         def select(context, result):
             for elem in result:
                 if elem.get(key) == value:
                     yield elem
-        return select
+        def select_negated(context, result):
+            for elem in result:
+                if (attr_value := elem.get(key)) is not None and attr_value != value:
+                    yield elem
+        return select_negated if '!=' in signature else select
     if signature == "-" and not re.match(r"\-?\d+$", predicate[0]):
         # [tag]
         tag = predicate[0]
@@ -270,8 +275,10 @@ def prepare_predicate(next, token):
                 if elem.find(tag) is not None:
                     yield elem
         return select
-    if signature == ".='" or (signature == "-='" and not re.match(r"\-?\d+$", predicate[0])):
+    if signature == ".='" or signature == ".!='" or (
-        # [.='value'] or [tag='value']
+            (signature == "-='" or signature == "-!='")
+            and not re.match(r"\-?\d+$", predicate[0])):
+        # [.='value'] or [tag='value'] or [.!='value'] or [tag!='value']
         tag = predicate[0]
         value = predicate[-1]
         if tag:
@@ -281,12 +288,22 @@ def prepare_predicate(next, token):
                         if "".join(e.itertext()) == value:
                             yield elem
                             break
+            def select_negated(context, result):
+                for elem in result:
+                    for e in elem.iterfind(tag):
+                        if "".join(e.itertext()) != value:
+                            yield elem
+                            break
         else:
             def select(context, result):
                 for elem in result:
                     if "".join(elem.itertext()) == value:
                         yield elem
-        return select
+            def select_negated(context, result):
+                for elem in result:
+                    if "".join(elem.itertext()) != value:
+                        yield elem
+        return select_negated if '!=' in signature else select
     if signature == "-" or signature == "-()" or signature == "-()-":
         # [index] or [last()] or [last()-index]
         if signature == "-":

Misc/NEWS.d/next/Library/2020-09-08-03-19-04.bpo-40624.0-gYfx.rst

@@ -0,0 +1 @@
+Added support for the XPath ``!=`` operator in xml.etree