Implemented an expanded syntax for cycler()

Author: WeatherGod

cycler.py

@@ -332,7 +332,61 @@ def simplify(self):
         return reduce(add, (cycler(k, v) for k, v in six.iteritems(trans)))
 
 
-def cycler(label, itr):
+def cycler(*args, **kwargs):
+    """
+    Create a new `Cycler` object from the combination of
+    positional arguments or keyword arguments.
+
+    cycler(arg)
+    cycler(label1, itr1[, label2, iter2[, ...]])
+    cycler(label1=itr1[, label2=iter2[, ...]])
+
+    Form 1 simply copies a given `Cycler` object.
+    Form 2 composes a `Cycler` as an outer product of the
+    pairs of label/iter.
+    Form 3 composes a `Cycler` as an inner product of the
+    pairs of keyword arguments.
+
+    Parameters
+    ----------
+    label : str
+        The property key.
+
+    itr : iterable
+        Finite length iterable of the property values.
+
+    Returns
+    -------
+    cycler : Cycler
+        New `Cycler` for the given property
+    """
+
+    if args and kwargs:
+        raise TypeError("cyl() can only accept positional OR keyword "
+                        "arguments -- not both.")
+    elif not args and not kwargs:
+        raise TypeError("cyl() must have positional OR keyword arguments")
+
+    if len(args) == 1:
+        if not isinstance(args[0], Cycler):
+            raise TypeError("If only one positional argument given, it must "
+                            " be a Cycler instance.")
+        return copy.copy(args[0])
+    elif len(args) > 1:
+        if (len(args) % 2) == 1:
+            raise TypeError("Positional arguments must be in pairs. Odd "
+                            " number of arguments found: %d" % len(args))
+        pairs = [(args[i], args[i+1]) for i in range(0, len(args), 2)]
+        op = mul
+
+    if kwargs:
+        pairs = six.iteritems(kwargs)
+        op = add
+
+    return reduce(op, (_cycler(k, v) for k, v in pairs))
+
+
+def _cycler(label, itr):
     """
     Create a new `Cycler` object from a property name and
     iterable of values.

test_cycler.py

@@ -28,6 +28,10 @@ def test_creation():
     yield _cycler_helper, c, 3, ['c'], [['r', 'g', 'b']]
     c = cycler('c', list('rgb'))
     yield _cycler_helper, c, 3, ['c'], [['r', 'g', 'b']]
+    c = cycler(c='rgb')
+    yield _cycler_helper, c, 3, ['c'], [['r', 'g', 'b']]
+    c = cycler(cycler('c', 'rgb'))
+    yield _cycler_helper, c, 3, ['c'], [['r', 'g', 'b']]
 
 
 def test_compose():
@@ -73,6 +77,33 @@ def test_constructor():
     c3 = cycler('c', c1)
     yield _cycler_helper, c3+c2, 3, ['c', 'ec'], [['r', 'g', 'b']]*2
 
+    # addition using cycler()
+    yield (_cycler_helper, cycler(c='rgb', lw=range(3)),
+            3, ['c', 'lw'], [list('rgb'), range(3)])
+    yield (_cycler_helper, cycler(lw=range(3), c='rgb'),
+            3, ['c', 'lw'], [list('rgb'), range(3)])
+    # Purposely mixing them
+    yield (_cycler_helper, cycler(c=range(3), lw=c1),
+            3, ['c', 'lw'], [range(3), list('rgb')])
+
+    # multiplication with cycler()
+    target = zip(*product(list('rgb'), range(3)))
+    yield (_cycler_helper, cycler('c', 'rgb', 'lw', range(3)),
+            9, ['c', 'lw'], target)
+
+    target = zip(*product(range(3), list('rgb')))
+    yield (_cycler_helper, cycler('lw', range(3), 'c', 'rgb'),
+            9, ['lw', 'c'], target)
+
+    target = zip(*product(range(15), list('rgb')))
+    yield (_cycler_helper, cycler('lw', range(15), 'c', 'rgb'),
+            45, ['lw', 'c'], target)
+
+    # Purposely mixing them
+    target = zip(*product(list('rgb'), range(15)))
+    yield (_cycler_helper, cycler('lw', c1, 'c', range(15)),
+            45, ['lw', 'c'], target)
+
 
 def test_failures():
     c1 = cycler('c', 'rgb')