Add del_in()

Closes #102

docs/cheatsheet.rst

@@ -33,7 +33,7 @@ Join                  :func:`merge` :func:`merge_with` :func:`join` :func:`join_
 Transform             :func:`walk` :func:`walk_keys` :func:`walk_values`
 Filter                :func:`select` :func:`select_keys` :func:`select_values` :func:`compact`
 Dicts :ref:`*<colls>` :func:`flip` :func:`zipdict` :func:`pluck` :func:`where` :func:`itervalues` :func:`iteritems` :func:`zip_values` :func:`zip_dicts` :func:`project` :func:`omit`
-Misc                  :func:`empty` :func:`get_in` :func:`set_in` :func:`update_in` :func:`has_path`
+Misc                  :func:`empty` :func:`get_in` :func:`set_in` :func:`update_in` :func:`del_in` :func:`has_path`
 ===================== ==============================================================
 
 

docs/colls.rst

@@ -220,6 +220,16 @@ Dict utils
         # -> {"a": {"cnt": 1}}
 
 
+.. function:: del_in(coll, path)
+
+    Creates a nested collection with ``path`` removed::
+
+        del_in({"a": [1, 2, 3]}, ["a", 1])
+        # -> {"a": [1, 3]}
+
+    Returns the collection as is if the path is missing.
+
+
 .. function:: has_path(coll, path)
 
     Checks if path exists in the given nested collection::

docs/descriptions.html

@@ -480,6 +480,10 @@
     <b>update_in<em>(coll, path, update, default=None)</em></b><br><br>
     Creates a copy of <em>coll</em> with a value updated at <em>path</em>.
 </div>
+<div name="del_in">
+    <b>del_in<em>(coll, path)</em></b><br><br>
+    Creates a copy of <em>coll</em> with <em>path</em> removed.
+</div>
 <div name="has_path">
     <b>has_path<em>(coll, path)</em></b><br><br>
     Tests whether <em>path</em> exists in a nested <em>coll</em>.

funcy/colls.py

@@ -19,7 +19,7 @@
            'is_distinct', 'all', 'any', 'none', 'one', 'some',
            'zipdict', 'flip', 'project', 'omit', 'zip_values', 'zip_dicts',
            'where', 'pluck', 'pluck_attr', 'invoke', 'lwhere', 'lpluck', 'lpluck_attr', 'linvoke',
-           'get_in', 'set_in', 'update_in', 'has_path']
+           'get_in', 'set_in', 'update_in', 'del_in', 'has_path']
 
 
 ### Generic ops
@@ -293,6 +293,24 @@ def update_in(coll, path, update, default=None):
         copy[path[0]] = update_in(copy.get(path[0], current_default), path[1:], update, default)
         return copy
 
+
+def del_in(coll, path):
+    """Creates a copy of coll with a nested key or index deleted."""
+    if not path:
+        return coll
+    try:
+        next_coll = coll[path[0]]
+    except (KeyError, IndexError):
+        return coll
+
+    copy = coll.copy()
+    if len(path) == 1:
+        del copy[path[0]]
+    else:
+        copy[path[0]] = del_in(next_coll, path[1:])
+    return copy
+
+
 def has_path(coll, path):
     """Checks if path exists in the given nested collection."""
     for p in path:

tests/test_colls.py

@@ -240,7 +240,6 @@ def test_get_in():
     assert get_in(d, ["a", "b"]) == "c"
     assert get_in(d, ["a", "f", "g"]) == "h"
 
-
 def test_get_in_list():
     assert get_in([1, 2], [0]) == 1
     assert get_in([1, 2], [3]) is None
@@ -263,14 +262,12 @@ def test_set_in():
     assert d3['e'] == {'f': 42}
     assert d3['a'] is d['a']
 
-
 def test_set_in_list():
     l = [{}, 1]
     l2 = set_in(l, [1], 7)
     assert l2 == [{}, 7]
     assert l2[0] is l[0]
 
-
 def test_update_in():
     d = {'c': []}
 
@@ -280,6 +277,14 @@ def test_update_in():
     assert d2['a']['b'] == 1
     assert d2['c'] is d['c']
 
+def test_del_in():
+    d = {'c': [1, 2, 3]}
+
+    assert del_in(d, []) is d
+    assert del_in(d, ['a', 'b']) is d
+    assert del_in(d, ['c', 1]) == {'c': [1, 3]}
+    with pytest.raises(TypeError): del_in(d, ['c', 'b'])
+
 def test_has_path():
     d = {
         "a": {