From 3e934e245b1294b88102deebea2ff06caae77640 Mon Sep 17 00:00:00 2001
From: Fabio Caccamo <fabio.caccamo@gmail.com>
Date: Tue, 2 Jul 2019 15:15:31 +0200
Subject: [PATCH] Added filter utility method.

---
 README.md                  |  7 +++++++
 README.rst                 |  7 +++++++
 benedict/dicts/__init__.py |  4 ++++
 benedict/dicts/utility.py  | 11 +++++++++++
 tests/test_utility_dict.py | 19 +++++++++++++++++++
 5 files changed, 48 insertions(+)

diff --git a/README.md b/README.md
index df75bf7..b61331d 100644
--- a/README.md
+++ b/README.md
@@ -64,6 +64,13 @@ s = d.dump_items(key=None)
 print(s)
 ```
 
+```python
+# Return a filtered dict using the given predicate function.
+# Predicate function receives key, value arguments and should return a bool value.
+predicate = lambda k, v: v is not None
+d.filter(predicate)
+```
+
 ```python
 # Get value by key or keypath trying to return it as bool.
 # Values like `1`, `true`, `yes`, `on`, `ok` will be returned as `True`.
diff --git a/README.rst b/README.rst
index be965d1..e86454d 100644
--- a/README.rst
+++ b/README.rst
@@ -75,6 +75,13 @@ API
     s = d.dump_items(key=None)
     print(s)
 
+.. code:: python
+
+    # Return a filtered dict using the given predicate function.
+    # Predicate function receives key, value arguments and should return a bool value.
+    predicate = lambda k, v: v is not None
+    d.filter(predicate)
+
 .. code:: python
 
     # Get value by key or keypath trying to return it as bool.
diff --git a/benedict/dicts/__init__.py b/benedict/dicts/__init__.py
index 406effd..bb37751 100644
--- a/benedict/dicts/__init__.py
+++ b/benedict/dicts/__init__.py
@@ -26,6 +26,10 @@ class benedict(KeypathDict, ParseDict, UtilityDict):
     def deepcopy(self):
         return super(benedict, self).deepcopy()
 
+    @benediction
+    def filter(self, func):
+        return super(benedict, self).filter(func)
+
     @classmethod
     @benediction
     def fromkeys(cls, sequence, value=None):
diff --git a/benedict/dicts/utility.py b/benedict/dicts/utility.py
index 015efa9..3186219 100644
--- a/benedict/dicts/utility.py
+++ b/benedict/dicts/utility.py
@@ -43,3 +43,14 @@ class UtilityDict(dict):
     def dump_items(self, key=None):
         return self.dump(self.get(key) if key else self)
 
+    def filter(self, predicate):
+        if not callable(predicate):
+            raise ValueError('predicate argument must be a callable.')
+        d = {}
+        keys = self.keys()
+        for key in keys:
+            val = self.get(key, None)
+            if predicate(key, val):
+                d[key] = val
+        return d
+
diff --git a/tests/test_utility_dict.py b/tests/test_utility_dict.py
index 95fcf94..685341f 100644
--- a/tests/test_utility_dict.py
+++ b/tests/test_utility_dict.py
@@ -154,3 +154,22 @@ class UtilityDictTestCase(unittest.TestCase):
         output = b.dump_items()
         self.assertEqual(output, expected_output)
 
+    def test_filter(self):
+        d = {
+            'a': 1,
+            'b': 2,
+            'c': '4',
+            'e': '5',
+            'f': 6,
+            'g': 7,
+        }
+        b = UtilityDict(d)
+        f = b.filter(lambda key, val: isinstance(val, int))
+        r = {
+            'a': 1,
+            'b': 2,
+            'f': 6,
+            'g': 7,
+        }
+        self.assertEqual(f, r)
+