make array.reshape compatible with numpy (apache#9790)

* make array.reshape compatible with numpy

* update

* add exception when both *args and **kwargs are specified

* update

python/mxnet/ndarray/ndarray.py

@@ -926,12 +926,12 @@ def _at(self, idx):
             self.handle, mx_uint(idx), ctypes.byref(handle)))
         return NDArray(handle=handle, writable=self.writable)
 
-    def reshape(self, shape):
+    def reshape(self, *shape, **kwargs):
         """Returns a **view** of this array with a new shape without altering any data.
 
         Parameters
         ----------
-        shape : tuple of int
+        shape : tuple of int, or n ints
             The new shape should not change the array size, namely
             ``np.prod(new_shape)`` should be equal to ``np.prod(self.shape)``.
 
@@ -960,6 +960,11 @@ def reshape(self, shape):
                [ 4.,  5.]], dtype=float32)
         >>> y = x.reshape((3,-1))
         >>> y.asnumpy()
+        array([[ 0.,  1.],
+               [ 2.,  3.],
+               [ 4.,  5.]], dtype=float32)
+        >>> y = x.reshape(3,2)
+        >>> y.asnumpy()
         array([[ 0.,  1.],
                [ 2.,  3.],
                [ 4.,  5.]], dtype=float32)
@@ -968,6 +973,17 @@ def reshape(self, shape):
         array([[-1., -1., -1.],
                [-1., -1., -1.]], dtype=float32)
         """
+        if len(shape) == 1 and isinstance(shape[0], (list, tuple)):
+            shape = shape[0]
+        elif not shape:
+            shape = kwargs.get('shape')
+            assert shape, "Shape must be provided."
+            if len(kwargs) != 1:
+                raise TypeError("Only 'shape' is supported as keyword argument. Got: {}."
+                                .format(', '.join(kwargs.keys())))
+        else:
+            assert not kwargs,\
+                "Specifying both positional and keyword arguments is not allowed in reshape."
         handle = NDArrayHandle()
 
         # Actual reshape

python/mxnet/ndarray/sparse.py

@@ -138,7 +138,7 @@ def _at(self, idx):
     def _slice(self, start, stop):
         raise NotSupportedForSparseNDArray(self._slice, None, start, stop)
 
-    def reshape(self, shape):
+    def reshape(self, *shape, **kwargs):
         raise NotSupportedForSparseNDArray(self.reshape, None, shape)
 
     @property

tests/python/unittest/test_ndarray.py

@@ -158,6 +158,11 @@ def test_ndarray_reshape():
                              [5, 6],
                              [7, 8]])
     assert same(tensor.reshape((-1, 2)).asnumpy(), true_res.asnumpy())
+    assert same(tensor.reshape(4, 2).asnumpy(), true_res.asnumpy())
+    assert same(tensor.reshape(-1, 2).asnumpy(), true_res.asnumpy())
+    true_res = mx.nd.arange(8) + 1
+    assert same(tensor.reshape(-1).asnumpy(), true_res.asnumpy())
+    assert same(tensor.reshape(8).asnumpy(), true_res.asnumpy())
 
 
 @with_seed()