Fix unexpected loading after print (#1724)

* Added test_ondisk_after_print in backend

* Remove an unintended change.

* remove conditional check. Use repr instead of print

Author: fujiisoup

doc/whats-new.rst

@@ -27,6 +27,8 @@ Bug fixes
   ``pandas.MultiIndex`` instead of a simple ``pandas.Index``
   (:issue:`1722`).  By `Benoit Bovy <https://github.com/benbovy>`_.
 
+- Fixed unexpected memory loading of backend arrays after ``print``.
+  (:issue:`1720`).  By `Keisuke Fujii <https://github.com/fujiisoup>`_.
 
 v0.10.0 rc2 (13 November 2017)
 ------------------------------

xarray/core/formatting.py

@@ -209,7 +209,7 @@ def summarize_variable(name, var, col_width, show_values=True,
     front_str = u'%s%s%s ' % (first_col, dims_str, var.dtype)
     if show_values:
         values_str = format_array_flat(var, max_width - len(front_str))
-    elif isinstance(var.data, dask_array_type):
+    elif isinstance(var._data, dask_array_type):
         values_str = short_dask_repr(var, show_dtype=False)
     else:
         values_str = u'...'

xarray/tests/test_backends.py

@@ -492,6 +492,13 @@ def test_dropna(self):
             actual = on_disk.dropna(dim='x')
             assert_identical(expected, actual)
 
+    def test_ondisk_after_print(self):
+        """ Make sure print does not load file into memory """
+        in_memory = create_test_data()
+        with self.roundtrip(in_memory) as on_disk:
+            repr(on_disk)
+            assert not on_disk['var1']._in_memory
+
 
 class CFEncodedDataTest(DatasetIOTestCases):