Implemented constantly in functoolz

doc/source/api.rst

@@ -60,6 +60,7 @@ Functoolz
 .. autosummary::
    complement
    compose
+   constantly
    curry
    do
    excepts

toolz/functoolz.py

@@ -621,10 +621,23 @@ def flip(func, a, b):
     return func(b, a)
 
 
-def return_none(exc):
-    """ Returns None.
+def constantly(v):
+    """Create function that always returns ``v``, independent of its input
+
+    >>> f = constantly(3)
+    >>> f(10)
+    3
+    >>> f({'any': 'obj'}, 'and', any='amt')
+    3
+    """
+    def inner(*args, **kwargs):
+        return v
+    return inner
+
+
+return_none = constantly(None)
+return_none.__doc__ = """Returns None.
     """
-    return None
 
 
 class excepts(object):

toolz/tests/test_functoolz.py

@@ -1,7 +1,8 @@
 import platform
 
-from toolz.functoolz import (thread_first, thread_last, memoize, curry,
-                             compose, pipe, complement, do, juxt, flip, excepts)
+from toolz.functoolz import (thread_first, thread_last, memoize, curry, compose,
+                             pipe, complement, do, juxt, flip, excepts,
+                             constantly)
 from operator import add, mul, itemgetter
 from toolz.utils import raises
 from functools import partial
@@ -576,6 +577,13 @@ def f(a, b):
     assert flip(f, 'a', 'b') == ('b', 'a')
 
 
+def test_constantly():
+    f = constantly(42)
+
+    assert f() == 42
+    assert f(2) == 42
+
+
 def test_excepts():
     # These are descriptors, make sure this works correctly.
     assert excepts.__name__ == 'excepts'