Test and document split_keys()

Author: Suor

docs/cheatsheet.rst

@@ -31,7 +31,7 @@ Collections
 ===================== ==============================================================
 Join                  :func:`merge` :func:`merge_with` :func:`join` :func:`join_with`
 Transform             :func:`walk` :func:`walk_keys` :func:`walk_values`
-Filter                :func:`select` :func:`select_keys` :func:`select_values` :func:`compact`
+Filter                :func:`select` :func:`select_keys` :func:`select_values` :func:`split_keys` :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:`get_lax` :func:`set_in` :func:`update_in` :func:`del_in` :func:`has_path`
 ===================== ==============================================================

docs/colls.rst

@@ -111,6 +111,18 @@ All functions in this section support :ref:`extended_fns`.
         # Construct a dict of methods
         select_values(inspect.isfunction, cls.__dict__)
 
+
+.. function:: split_keys(pred, coll)
+
+    Splits a dictionary into two based on a predicate applied to its keys.
+
+    Say, you can separate custom HTTP headers from standard ones::
+
+        custom, standard = split_keys(r'^X-', headers)
+        # custom -> {'X-Custom-Header': 'value'}
+        # standard -> {'Content-Type': 'application/json', ...}
+
+
 .. function:: compact(coll)
 
     Removes falsy values from given collection. When compacting a dict all keys with falsy values are removed.

docs/descriptions.html

@@ -428,6 +428,11 @@
     Select part of <em>coll</em> with values passing <em>pred</em>.<br>
     Works with dicts and collections of pairs.
 </div>
+<div name="split_keys">
+    <b>split_keys<em>(pred, coll)</em></b><br><br>
+    Splits <em>coll</em> part with keys passing <em>pred</em><br>
+    from the one with remaining pairs.
+</div>
 <div name="compact">
     <b>compact<em>(coll)</em></b><br><br>
     Removes falsy values from given collection.

tests/test_colls.py

@@ -151,6 +151,13 @@ def test_select_values():
     assert select_values(r'a', {1: 'a', 2: 'b'}) == {1: 'a'}
 
 
+def test_split_keys():
+    d = {'a': 1, 'b': 2, 1: 3, 2: 4}
+    yes, no = split_keys(lambda k: isinstance(k, str), d)
+    assert yes == {'a': 1, 'b': 2}
+    assert no == {1: 3, 2: 4}
+
+
 def test_compact():
     assert eq(compact([0, 1, None, 3]), [1, 3])
     assert eq(compact((0, 1, None, 3)), (1, 3))