added step in slice

Author: Laurent PINSON

jsonpath_ng/parser.py

@@ -176,8 +176,9 @@ def p_slice_any(self, p):
         p[0] = Slice()
 
     def p_slice(self, p): # Currently does not support `step`
-        "slice : maybe_int ':' maybe_int"
-        p[0] = Slice(start=p[1], end=p[3])
+        """slice : maybe_int ':' maybe_int
+                 | maybe_int ':' maybe_int ':' maybe_int """
+        p[0] = Slice(*p[1::2])
 
     def p_maybe_int(self, p):
         """maybe_int : NUMBER

tests/test_jsonpath.py

@@ -140,7 +140,11 @@ def test_slice_value(self):
         self.check_cases([('[*]', [1, 2, 3], [1, 2, 3]),
                           ('[*]', xrange(1, 4), [1, 2, 3]),
                           ('[1:]', [1, 2, 3, 4], [2, 3, 4]),
-                          ('[:2]', [1, 2, 3, 4], [1, 2])
+                          ('[:2]', [1, 2, 3, 4], [1, 2]),
+                          ('[:3:2]', [1, 2, 3, 4], [1, 3]),
+                          ('[1::2]', [1, 2, 3, 4], [2, 4]),
+                          ('[1:5:3]', [1, 2, 3, 4, 5], [2, 5]),
+                          ('[::-2]', [1, 2, 3, 4, 5], [5, 3, 1]),
         ])
 
         # Funky slice hacks
@@ -226,7 +230,11 @@ def test_index_paths(self):
 
     def test_slice_paths(self):
         self.check_paths([ ('[*]', [1, 2, 3], ['[0]', '[1]', '[2]']),
-                           ('[1:]', [1, 2, 3, 4], ['[1]', '[2]', '[3]']) 
+                           ('[1:]', [1, 2, 3, 4], ['[1]', '[2]', '[3]']),
+                           ('[1:3]', [1, 2, 3, 4], ['[1]', '[2]']),
+                           ('[1::2]', [1, 2, 3, 4], ['[1]', '[3]']),
+                           ('[::-1]', [1, 2, 3], ['[2]', '[1]', '[0]']),
+                           ('[1:6:3]', xrange(10), ['[1]', '[4]']),
         ])
 
     def test_child_paths(self):