kennknowles · kennknowles · Oct 5, 2016 · Jul 13, 2015
diff --git a/jsonpath_rw/jsonpath.py b/jsonpath_rw/jsonpath.py
@@ -227,6 +227,11 @@ def find(self, datum):
                 if not isinstance(subdata, AutoIdForDatum)
                 for submatch in self.right.find(subdata)]
 
+    def update(self, data, val):
+        for datum in self.left.find(data):
+            self.right.update(datum.value, val)
+        return data
+
     def __eq__(self, other):
         return isinstance(other, Child) and self.left == other.left and self.right == other.right
 
@@ -274,6 +279,11 @@ def __init__(self, left, right):
     def find(self, data):
         return [subdata for subdata in self.left.find(data) if self.right.find(subdata)]
 
+    def update(self, data, val):
+        for datum in self.find(data):
+            datum.path.update(data, val)
+        return data
+
     def __str__(self):
         return '%s where %s' % (self.left, self.right)
 
@@ -329,6 +339,11 @@ def match_recursively(datum):
     def is_singular():
         return False
 
+    def update(self, data, val):
+        for datum in self.left.find(data):
+            self.right.update(datum.value, val)
+        return data
+
     def __str__(self):
         return '%s..%s' % (self.left, self.right)
 
@@ -415,6 +430,11 @@ def find(self, datum):
                  for field_datum in [self.get_field_datum(datum, field) for field in self.reified_fields(datum)]
                  if field_datum is not None]
 
+    def update(self, data, val):
+        for field in self.reified_fields(DatumInContext.wrap(data)):
+            data[field] = val
+        return data
+
     def __str__(self):
         return ','.join(map(str, self.fields))
 
@@ -445,6 +465,10 @@ def find(self, datum):
         else:
             return []
 
+    def update(self, data, val):
+        data[self.index] = val
+        return data
+
     def __eq__(self, other):
         return isinstance(other, Index) and self.index == other.index
 
@@ -495,6 +519,11 @@ def find(self, datum):
         else:
             return [DatumInContext(datum.value[i], path=Index(i), context=datum) for i in range(0, len(datum.value))[self.start:self.end:self.step]]
 
+    def update(self, data, val):
+        for datum in self.find(data):
+            datum.path.update(data, val)
+        return data
+
     def __str__(self):
         if self.start == None and self.end == None and self.step == None:
             return '[*]'

diff --git a/tests/test_update.py b/tests/test_update.py
@@ -0,0 +1,67 @@
+from __future__ import unicode_literals, print_function, absolute_import, division, generators, nested_scopes
+
+import unittest
+import logging
+
+from jsonpath_rw.parser import parse
+
+
+class TestUpdate(unittest.TestCase):
+
+    @classmethod
+    def setup_class(cls):
+        logging.basicConfig()
+
+    def check_update_cases(self, test_cases):
+        for original, expr_str, value, expected in test_cases:
+            print('parse(%r).update(%r, %r) =?= %r'
+                  % (expr_str, original, value, expected))
+            expr = parse(expr_str)
+            actual = expr.update(original, value)
+            assert actual == expected
+
+    def test_update_root(self):
+        self.check_update_cases([
+            ('foo', '$', 'bar', 'bar')
+        ])
+
+    def test_update_this(self):
+        self.check_update_cases([
+            ('foo', '`this`', 'bar', 'bar')
+        ])
+
+    def test_update_fields(self):
+        self.check_update_cases([
+            ({'foo': 1}, 'foo', 5, {'foo': 5}),
+            ({}, 'foo', 1, {'foo': 1}),
+            ({'foo': 1, 'bar': 2}, '$.*', 3, {'foo': 3, 'bar': 3})
+        ])
+
+    def test_update_child(self):
+        self.check_update_cases([
+            ({'foo': 'bar'}, '$.foo', 'baz', {'foo': 'baz'}),
+            ({'foo': {'bar': 1}}, 'foo.bar', 'baz', {'foo': {'bar': 'baz'}})
+        ])
+
+    def test_update_where(self):
+        self.check_update_cases([
+            ({'foo': {'bar': {'baz': 1}}, 'bar': {'baz': 2}},
+             '*.bar where baz', 5, {'foo': {'bar': 5}, 'bar': {'baz': 2}})
+        ])
+
+    def test_update_descendants(self):
+        self.check_update_cases([
+            ({'foo': {'bar': 1, 'flag': 1}, 'baz': {'bar': 2}},
+             '* where flag .. bar', 3,
+             {'foo': {'bar': 3, 'flag': 1}, 'baz': {'bar': 2}})
+        ])
+
+    def test_update_index(self):
+        self.check_update_cases([
+            (['foo', 'bar', 'baz'], '[0]', 'test', ['test', 'bar', 'baz'])
+        ])
+
+    def test_update_slice(self):
+        self.check_update_cases([
+            (['foo', 'bar', 'baz'], '[0:2]', 'test', ['test', 'test', 'baz'])
+        ])