issues: 178111738

Following creation of a new conda environment:

bash cd /tmp conda create -n test_xarray27 python=2.7 -y source activate test_xarray27 conda install matplotlib dask bottleneck pytest -y git clone git@github.com:pydata/xarray.git cd xarray git co master python setup.py develop py.test

returns

``` bash ┌─[pwolfram][shapiro][/tmp/xarray][10:34][±][master ✓] └─▪ py.test =========================================================================================================== test session starts ============================================================================================================ platform darwin -- Python 2.7.10 -- py-1.4.27 -- pytest-2.7.1 rootdir: /private/tmp/xarray, inifile: setup.cfg collected 1028 items

xarray/test/test_backends.py ............................................................................................................................................................................................sssssssssssssssssssssssssssssssssssss.........sssssssssssssssssssssssss...... xarray/test/test_combine.py .............. xarray/test/test_conventions.py .............................................s............ xarray/test/test_dask.py ..........F.................... xarray/test/test_dataarray.py ...........................................................s...................................................s............. xarray/test/test_dataset.py ............................................................................................................................................. xarray/test/test_extensions.py .... xarray/test/test_formatting.py ......... xarray/test/test_groupby.py ... xarray/test/test_indexing.py ......... xarray/test/test_merge.py .............. xarray/test/test_ops.py ............. xarray/test/test_plot.py .............................................................................................................................................................................................. xarray/test/test_tutorial.py s xarray/test/test_ufuncs.py .... xarray/test/test_utils.py ................... xarray/test/test_variable.py ............................................................................................................................... xarray/test/test_xray.py .

================================================================================================================= FAILURES ================================================================================================================= _______________ TestVariable.test_reduce _______________

self = <xarray.test.test_dask.TestVariable testMethod=test_reduce>

def test_reduce(self):
    u = self.eager_var
    v = self.lazy_var
    self.assertLazyAndAllClose(u.mean(), v.mean())
    self.assertLazyAndAllClose(u.std(), v.std())

  self.assertLazyAndAllClose(u.argmax(dim='x'), v.argmax(dim='x'))

xarray/test/test_dask.py:145:

---

xarray/core/common.py:16: in wrapped_func skipna=skipna, allow_lazy=True, kwargs) xarray/core/variable.py:899: in reduce axis=axis, kwargs) xarray/core/ops.py:308: in f return func(values, axis=axis, kwargs) xarray/core/ops.py:64: in f return getattr(module, name)(*args, kwargs) /Users/pwolfram/anaconda/lib/python2.7/site-packages/dask/array/reductions.py:542: in _ return arg_reduction(x, chunk, combine, agg, axis, split_every)

---

x = dask.array<from-ar..., shape=(4, 6), dtype=float64, chunksize=(2, 2)>, chunk = <functools.partial object at 0x115f3ef70>, combine = <functools.partial object at 0x115f3efc8>, agg = <functools.partial object at 0x115f4b050> axis = (0,), split_every = None

def arg_reduction(x, chunk, combine, agg, axis=None, split_every=None):
    """Generic function for argreduction.

    Parameters
    ----------
    x : Array
    chunk : callable
        Partialed ``arg_chunk``.
    combine : callable
        Partialed ``arg_combine``.
    agg : callable
        Partialed ``arg_agg``.
    axis : int, optional
    split_every : int or dict, optional
    """
    if axis is None:
        axis = tuple(range(x.ndim))
        ravel = True
    elif isinstance(axis, int):
        if axis < 0:
            axis += x.ndim
        if axis < 0 or axis >= x.ndim:
            raise ValueError("axis entry is out of bounds")
        axis = (axis,)
        ravel = x.ndim == 1
    else:
        raise TypeError("axis must be either `None` or int, "
                        "got '{0}'".format(axis))

    # Map chunk across all blocks
    name = 'arg-reduce-chunk-{0}'.format(tokenize(chunk, axis))
    old = x.name
    keys = list(product(*map(range, x.numblocks)))
    offsets = list(product(*(accumulate(operator.add, bd[:-1], 0)

                           for bd in x.chunks)))

E TypeError: type object argument after * must be a sequence, not generator

/Users/pwolfram/anaconda/lib/python2.7/site-packages/dask/array/reductions.py:510: TypeError ============================================================================================ 1 failed, 961 passed, 66 skipped in 52.49 seconds =============================================================================================

```

cc @shoyer