add MethodCaller #31

docs/reference.md

@@ -514,6 +514,23 @@ namespace()
 
 ```
 
+## MethodCaller
+
+```py
+>>> class K:
+...     def hello(self):
+...         return 'hello'
+...     def increment(self, i, add=1):
+...         return i + add
+>>> k = K()
+>>> k | MethodCaller('hello')
+'hello'
+>>> k | MethodCaller('increment', 1)
+2
+>>> k | MethodCaller('increment', 1, add=2)
+3
+
+```
 
 ## Unique
 

pipe21.py

@@ -60,6 +60,7 @@ class MapDelItem   (B): __ror__ = lambda self, it: it | Map(lambda kv: kv | DelI
 class MapGetAttr   (B): __ror__ = lambda self, it: it | Map(lambda kv: kv | GetAttr(self.f))
 class MapSetAttr   (B): __ror__ = lambda self, it: it | Map(lambda kv: kv | SetAttr(self.f, self.args[0]))
 class MapDelAttr   (B): __ror__ = lambda self, it: it | Map(lambda kv: kv | DelAttr(self.f))
+class MethodCaller (B): __ror__ = lambda self, x: operator.methodcaller(self.f, *self.args, **self.kw)(x)
 
 
 class Unique(B):

tests/pipe_test.py

@@ -366,6 +366,21 @@ def test_descriptors():
     assert [SimpleNamespace(a='b')] | MapDelAttr('a') | Pipe(list) == [SimpleNamespace()]
 
 
+class K:
+    def hello(self):
+        return 'hello'
+
+    def increment(self, i, add=1):
+        return i + add
+
+
+def test_methodcaller():
+    k = K()
+    assert k | MethodCaller('hello') == 'hello'
+    assert k | MethodCaller('increment', 1) == 2
+    assert k | MethodCaller('increment', 1, add=2) == 3
+
+
 @pytest.mark.parametrize(
     ('seq', 'key', 'expected'), [
         ([0, 1, 1, 2], None, [0, 1, 2]),