From cc5f39ae919f4a5202f9bab5017d8c23cc6b4020 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Fri, 8 Jun 2018 17:40:38 -0400
Subject: [PATCH 01/15] Removed dead code, added support to set center at min
 values, added test case

---
 yt/data_objects/data_containers.py            | 30 +++----------------
 yt/data_objects/tests/test_data_containers.py |  0
 yt/data_objects/tests/test_spheres.py         | 20 ++++++++++---
 3 files changed, 20 insertions(+), 30 deletions(-)
 create mode 100644 yt/data_objects/tests/test_data_containers.py

diff --git a/yt/data_objects/data_containers.py b/yt/data_objects/data_containers.py
index a318db840ba..967a2c1bcc6 100644
--- a/yt/data_objects/data_containers.py
+++ b/yt/data_objects/data_containers.py
@@ -80,19 +80,6 @@ def force_array(item, shape):
         else:
             return np.zeros(shape, dtype='bool')
 
-def restore_field_information_state(func):
-    """
-    A decorator that takes a function with the API of (self, grid, field)
-    and ensures that after the function is called, the field_parameters will
-    be returned to normal.
-    """
-    def save_state(self, grid, field=None, *args, **kwargs):
-        old_params = grid.field_parameters
-        grid.field_parameters = self.field_parameters
-        tr = func(self, grid, field, *args, **kwargs)
-        grid.field_parameters = old_params
-        return tr
-    return save_state
 
 def sanitize_weight_field(ds, field, weight):
     field_object = ds._get_field_info(field)
@@ -215,6 +202,10 @@ def _set_center(self, center):
                 self.center = self.ds.find_max(("gas", "density"))[1]
             elif center.startswith("max_"):
                 self.center = self.ds.find_max(center[4:])[1]
+            elif center.lower() == "min":
+                self.center = self.ds.find_min(("gas", "density"))[1]
+            elif center.startswith("min_"):
+                self.center = self.ds.find_min(center[4:])[1]
         else:
             self.center = self.ds.arr(center, 'code_length', dtype='float64')
         self.set_field_parameter('center', self.center)
@@ -1990,20 +1981,7 @@ def extract_connected_sets(self, field, num_levels, min_val, max_val,
                     {'contour_slices_%s' % contour_key: cids})
         return cons, contours
 
-    def paint_grids(self, field, value, default_value=None):
-        """
-        This function paints every cell in our dataset with a given *value*.
-        If default_value is given, the other values for the given in every grid
-        are discarded and replaced with *default_value*.  Otherwise, the field is
-        mandated to 'know how to exist' in the grid.
 
-        Note that this only paints the cells *in the dataset*, so cells in grids
-        with child cells are left untouched.
-        """
-        for grid in self._grids:
-            if default_value is not None:
-                grid[field] = np.ones(grid.ActiveDimensions)*default_value
-            grid[field][self._get_point_indices(grid)] = value
 
     def volume(self):
         """
diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/yt/data_objects/tests/test_spheres.py b/yt/data_objects/tests/test_spheres.py
index b6d2b3318b3..3ca85007495 100644
--- a/yt/data_objects/tests/test_spheres.py
+++ b/yt/data_objects/tests/test_spheres.py
@@ -1,10 +1,9 @@
 import numpy as np
+from numpy.testing import assert_array_equal
 
 from yt.data_objects.profiles import create_profile
-from yt.testing import \
-    fake_random_ds, \
-    assert_equal, \
-    periodicity_cases
+from yt.testing import fake_random_ds, assert_equal, periodicity_cases
+
 
 def setup():
     from yt.config import ytcfg
@@ -65,3 +64,16 @@ def test_domain_sphere():
         for f in _fields_to_compare:
             sp[f].sort()
             assert_equal(sp[f], ref_sp[f])
+
+def test_sphere_center():
+    ds = fake_random_ds(16, nprocs=8,
+                        fields=("density", "temperature", "velocity_x"))
+
+    # Test if we obtain same center in different ways
+    sp1 = ds.sphere("max", (0.25, 'unitary'))
+    sp2 = ds.sphere("max_density", (0.25, 'unitary'))
+    assert_array_equal(sp1.center, sp2.center)
+
+    sp1 = ds.sphere("min", (0.25, 'unitary'))
+    sp2 = ds.sphere("min_density", (0.25, 'unitary'))
+    assert_array_equal(sp1.center, sp2.center)

From 3fca6bcec57cac6e885aa7cbe5a743c73230eedc Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 17:15:30 -0400
Subject: [PATCH 02/15] update fiel i/o using context mgr; fixed to_frb

---
 yt/data_objects/data_containers.py | 36 +++++++++++++++---------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/yt/data_objects/data_containers.py b/yt/data_objects/data_containers.py
index 967a2c1bcc6..ee43b73a83d 100644
--- a/yt/data_objects/data_containers.py
+++ b/yt/data_objects/data_containers.py
@@ -80,7 +80,6 @@ def force_array(item, shape):
         else:
             return np.zeros(shape, dtype='bool')
 
-
 def sanitize_weight_field(ds, field, weight):
     field_object = ds._get_field_info(field)
     if weight is None:
@@ -420,16 +419,18 @@ def _parameter_iterate(self, seq):
     def write_out(self, filename, fields=None, format="%0.16e"):
         if fields is None: fields=sorted(self.field_data.keys())
         if self._key_fields is None: raise ValueError
-        field_order = self._key_fields[:]
-        for field in field_order: self[field]
-        field_order += [field for field in fields if field not in field_order]
-        fid = open(filename,"w")
-        fid.write("\t".join(["#"] + field_order + ["\n"]))
-        field_data = np.array([self.field_data[field] for field in field_order])
-        for line in range(field_data.shape[1]):
-            field_data[:,line].tofile(fid, sep="\t", format=format)
-            fid.write("\n")
-        fid.close()
+        field_order = self._determine_fields(self._key_fields)
+        for field in field_order:
+            self[field]
+        field_order += [self._determine_fields(field)[0] for field in fields
+                        if field not in field_order]
+        field_header = [str(f) for f in field_order]
+        with open(filename,"w") as fid:
+            fid.write("\t".join(["#"] + field_header + ["\n"]))
+            field_data = np.array([self.field_data[field] for field in field_order])
+            for line in range(field_data.shape[1]):
+                field_data[:,line].tofile(fid, sep="\t", format=format)
+                fid.write("\n")
 
     def save_object(self, name, filename = None):
         """
@@ -438,11 +439,10 @@ def save_object(self, name, filename = None):
         :meth:`yt.data_objects.api.GridIndex.save_object`.
         """
         if filename is not None:
-            ds = shelve.open(filename, protocol=-1)
-            if name in ds:
-                mylog.info("Overwriting %s in %s", name, filename)
-            ds[name] = self
-            ds.close()
+            with shelve.open(filename, protocol=-1) as ds:
+                if name in ds:
+                    mylog.info("Overwriting %s in %s", name, filename)
+                ds[name] = self
         else:
             self.index.save_object(self, name)
 
@@ -1664,8 +1664,8 @@ def to_frb(self, width, resolution, center=None, height=None,
                     "Currently we only support images centered at R=0. " +
                     "We plan to generalize this in the near future")
             from yt.visualization.fixed_resolution import CylindricalFixedResolutionBuffer
-            if iterable(width):
-                radius = max(width)
+            if isinstance(width, tuple):
+               radius = width[0]
             else:
                 radius = width
             if iterable(resolution): resolution = max(resolution)

From ef197194a9e28b7155d1b5617c32d727ddb36261 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 17:18:19 -0400
Subject: [PATCH 03/15] Fixed YTSmoothedCoveringGrid __init__

---
 yt/data_objects/construction_data_containers.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/yt/data_objects/construction_data_containers.py b/yt/data_objects/construction_data_containers.py
index 0d5b21d4f07..135fb6942be 100644
--- a/yt/data_objects/construction_data_containers.py
+++ b/yt/data_objects/construction_data_containers.py
@@ -922,7 +922,8 @@ def __init__(self, *args, **kwargs):
         self._final_start_index = self.global_startindex
 
     def _setup_data_source(self, level_state = None):
-        if level_state is None: return
+        if level_state is None:
+            return super(YTSmoothedCoveringGrid, self)._setup_data_source()
         # We need a buffer region to allow for zones that contribute to the
         # interpolation but are not directly inside our bounds
         level_state.data_source = self.ds.region(

From bf72557c370b6d575f4d389f6ffa893fd5bc6300 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 17:29:58 -0400
Subject: [PATCH 04/15] Added test cases

---
 yt/data_objects/tests/test_clone.py           |   7 ++
 yt/data_objects/tests/test_connected_sets.py  |  21 ++--
 yt/data_objects/tests/test_data_containers.py | 114 ++++++++++++++++++
 3 files changed, 130 insertions(+), 12 deletions(-)

diff --git a/yt/data_objects/tests/test_clone.py b/yt/data_objects/tests/test_clone.py
index e44bac092a0..8b3087b2b91 100644
--- a/yt/data_objects/tests/test_clone.py
+++ b/yt/data_objects/tests/test_clone.py
@@ -22,3 +22,10 @@ def test_clone_sphere():
     sp1["density"]
 
     assert_array_equal(sp0["density"], sp1["density"])
+
+def test_clone_cut_region():
+    ds = fake_random_ds(64, nprocs=4, fields=("density", "temperature"))
+    dd = ds.all_data()
+    reg1 = dd.cut_region(["obj['temperature'] > 0.5", "obj['density'] < 0.75"])
+    reg2 = reg1.clone()
+    assert_array_equal(reg1['density'], reg2['density'])
diff --git a/yt/data_objects/tests/test_connected_sets.py b/yt/data_objects/tests/test_connected_sets.py
index 284cf0f4957..af5aa034b38 100644
--- a/yt/data_objects/tests/test_connected_sets.py
+++ b/yt/data_objects/tests/test_connected_sets.py
@@ -1,14 +1,11 @@
-from yt.utilities.answer_testing.level_sets_tests import \
-    ExtractConnectedSetsTest
-from yt.utilities.answer_testing.framework import \
-    requires_ds, \
-    data_dir_load
+from yt.testing import fake_random_ds
+from yt.utilities.answer_testing.level_sets_tests import ExtractConnectedSetsTest
 
-g30 = "IsolatedGalaxy/galaxy0030/galaxy0030"
-@requires_ds(g30, big_data=True)
 def test_connected_sets():
-    ds = data_dir_load(g30)
-    data_source = ds.disk([0.5, 0.5, 0.5], [0., 0., 1.],
-                          (8, 'kpc'), (1, 'kpc'))
-    yield ExtractConnectedSetsTest(g30, data_source, ("gas", "density"),
-                                   5, 1e-24, 8e-24)
+    ds = fake_random_ds(16, nprocs=8, particles=16**3)
+    data_source = ds.disk([0.5, 0.5, 0.5], [0., 0., 1.], (8, 'kpc'), (1, 'kpc'))
+    field = ("gas", "density")
+    min_val, max_val = data_source[field].min()/2, data_source[field].max()/2
+    data_source.extract_connected_sets(field, 5, min_val, max_val,
+                                       log_space=True, cumulative=True)
+    yield ExtractConnectedSetsTest(ds, data_source, field, 5, min_val, max_val)
diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index e69de29bb2d..bbcd7434734 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -0,0 +1,114 @@
+import shelve
+
+import numpy as np
+from nose.tools import assert_raises
+from numpy.testing import assert_array_equal
+
+from yt.data_objects.data_containers import YTDataContainer
+from yt.testing import assert_equal, fake_random_ds, fake_amr_ds, fake_particle_ds
+from yt.utilities.exceptions import YTFieldNotFound
+
+
+def test_yt_data_container():
+    # Test if ds could be None
+    with assert_raises(RuntimeError) as err:
+        YTDataContainer(None, None)
+    desired = 'Error: ds must be set either through class type or parameter' \
+              ' to the constructor'
+    assert_equal(str(err.exception), desired)
+
+    # Test if field_data key exists
+    ds = fake_random_ds(5)
+    proj = ds.proj("density", 0, data_source=ds.all_data())
+    assert_equal(proj.has_key('px'), True)
+    assert_equal(proj.has_key('pz'), False)
+
+    # Delete the key and check if exits
+    proj.__delitem__('px')
+    assert_equal(proj.has_key('px'), False)
+    proj.__delitem__('density')
+    assert_equal(proj.has_key('density'), False)
+
+    # Delete a non-existent field
+    with assert_raises(YTFieldNotFound) as ex:
+        proj.__delitem__('p_mass')
+    desired = "Could not find field '('stream', 'p_mass')' in UniformGridData."
+    assert_equal(str(ex.exception), desired)
+
+    # Test the convert method
+    assert_equal(proj.convert('HydroMethod'), -1)
+
+def test_write_out():
+    filename = "sphere.txt"
+    ds = fake_particle_ds()
+    sp = ds.sphere(ds.domain_center, 0.25)
+    sp.write_out(filename)
+
+    with open(filename, "r") as file:
+        file_row_1 = file.readline()
+        file_row_2 = file.readline()
+        file_row_2 = np.array(file_row_2.split('\t'), dtype=np.float64)
+    _keys = [str(k) for k in sp.field_data.keys()]
+    _keys = "\t".join(["#"] + _keys + ["\n"])
+    _data = [sp.field_data[k][0] for k in sp.field_data.keys()]
+
+    assert_equal(_keys, file_row_1)
+    assert_array_equal(_data, file_row_2)
+
+def test_save_object():
+    ds = fake_particle_ds()
+    sp = ds.sphere(ds.domain_center, 0.25)
+    sp.save_object("my_sphere_1", filename="test_save_obj")
+    with shelve.open("test_save_obj", protocol=-1) as obj:
+        loaded_sphere = obj["my_sphere_1"][1]
+    assert_array_equal(loaded_sphere.center, sp.center)
+    assert_equal(loaded_sphere.radius, sp.radius)
+
+    sp.save_object("my_sphere_2")
+
+def test_to_dataframe():
+    fields = ["density", "velocity_z"]
+    ds = fake_random_ds(6)
+    dd = ds.all_data()
+    df1 = dd.to_dataframe(fields)
+    assert_array_equal(dd[fields[0]], df1[fields[0]])
+    assert_array_equal(dd[fields[1]], df1[fields[1]])
+
+def test_std():
+    ds = fake_random_ds(3)
+    ds.all_data().std('density', weight="velocity_z")
+
+def test_to_frb():
+    ds = fake_amr_ds(fields=["density", "cell_mass"], geometry="cylindrical",
+                     particles=16**3)
+    proj = ds.proj("density", weight_field="cell_mass", axis=1,
+                   data_source=ds.all_data())
+    proj.to_frb((1.0, 'unitary'), 64)
+
+def test_extract_isocontours():
+    # Test isocontour properties for AMRGridData
+    ds = fake_amr_ds(fields=["density", "cell_mass"], particles=16**3)
+    dd = ds.all_data()
+    rho = dd.quantities["WeightedAverageQuantity"]("density",
+                                                   weight="cell_mass")
+    dd.extract_isocontours("density", rho, "triangles.obj", True)
+    dd.calculate_isocontour_flux("density", rho, "x", "y", "z",
+                                 "dx")
+
+    # Test error in case of ParticleData
+    ds = fake_particle_ds()
+    dd = ds.all_data()
+    rho = dd.quantities["WeightedAverageQuantity"]("particle_velocity_x",
+                                                   weight="particle_mass")
+    with assert_raises(NotImplementedError):
+        dd.extract_isocontours("density", rho, sample_values='x')
+
+def test_extract_connected_sets():
+
+    ds = fake_random_ds(16, nprocs=8, particles=16 ** 3)
+    data_source = ds.disk([0.5, 0.5, 0.5], [0., 0., 1.], (8, 'kpc'), (1, 'kpc'))
+    field = ("gas", "density")
+    min_val, max_val = data_source[field].min() / 2, data_source[field].max() / 2
+
+    data_source.extract_connected_sets(field, 3, min_val, max_val,
+                                              log_space=True, cumulative=True)

From 680fb9213d8e87c2531a7038191189ae112102d3 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 17:51:06 -0400
Subject: [PATCH 05/15] fixed flake8 warnings

---
 yt/data_objects/tests/test_data_containers.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index bbcd7434734..382afe66e4c 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -20,14 +20,14 @@ def test_yt_data_container():
     # Test if field_data key exists
     ds = fake_random_ds(5)
     proj = ds.proj("density", 0, data_source=ds.all_data())
-    assert_equal(proj.has_key('px'), True)
-    assert_equal(proj.has_key('pz'), False)
+    assert_equal('px' in proj.keys(), True)
+    assert_equal('pz' in proj.keys(), False)
 
     # Delete the key and check if exits
     proj.__delitem__('px')
-    assert_equal(proj.has_key('px'), False)
+    assert_equal('px' in proj.keys(), False)
     proj.__delitem__('density')
-    assert_equal(proj.has_key('density'), False)
+    assert_equal('density' in proj.keys(), False)
 
     # Delete a non-existent field
     with assert_raises(YTFieldNotFound) as ex:

From 218e33c8ebc1a1f1e07c5352ea625d71f79901c6 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 18:57:34 -0400
Subject: [PATCH 06/15] Revert the use of context manager due to python 2

---
 yt/data_objects/data_containers.py | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/yt/data_objects/data_containers.py b/yt/data_objects/data_containers.py
index ee43b73a83d..72c4ccdaf79 100644
--- a/yt/data_objects/data_containers.py
+++ b/yt/data_objects/data_containers.py
@@ -419,18 +419,17 @@ def _parameter_iterate(self, seq):
     def write_out(self, filename, fields=None, format="%0.16e"):
         if fields is None: fields=sorted(self.field_data.keys())
         if self._key_fields is None: raise ValueError
-        field_order = self._determine_fields(self._key_fields)
-        for field in field_order:
-            self[field]
-        field_order += [self._determine_fields(field)[0] for field in fields
-                        if field not in field_order]
+        field_order = self._key_fields[:]
+        for field in field_order: self[field]
+        field_order += [field for field in fields if field not in field_order]
+        fid = open(filename,"w")
         field_header = [str(f) for f in field_order]
-        with open(filename,"w") as fid:
-            fid.write("\t".join(["#"] + field_header + ["\n"]))
-            field_data = np.array([self.field_data[field] for field in field_order])
-            for line in range(field_data.shape[1]):
-                field_data[:,line].tofile(fid, sep="\t", format=format)
-                fid.write("\n")
+        fid.write("\t".join(["#"] + field_header + ["\n"]))
+        field_data = np.array([self.field_data[field] for field in field_order])
+        for line in range(field_data.shape[1]):
+            field_data[:,line].tofile(fid, sep="\t", format=format)
+            fid.write("\n")
+        fid.close()
 
     def save_object(self, name, filename = None):
         """
@@ -439,10 +438,11 @@ def save_object(self, name, filename = None):
         :meth:`yt.data_objects.api.GridIndex.save_object`.
         """
         if filename is not None:
-            with shelve.open(filename, protocol=-1) as ds:
-                if name in ds:
-                    mylog.info("Overwriting %s in %s", name, filename)
-                ds[name] = self
+            ds = shelve.open(filename, protocol=-1)
+            if name in ds:
+                mylog.info("Overwriting %s in %s", name, filename)
+            ds[name] = self
+            ds.close()
         else:
             self.index.save_object(self, name)
 

From e2b4d70ea34731eff6b1cf30760d283c199fe838 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 19:43:22 -0400
Subject: [PATCH 07/15] Fixed Pandas test, sort writing to file

---
 yt/data_objects/data_containers.py            |  2 +-
 yt/data_objects/tests/test_data_containers.py | 21 ++++++++++++-------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/yt/data_objects/data_containers.py b/yt/data_objects/data_containers.py
index 72c4ccdaf79..d0c8d5d295a 100644
--- a/yt/data_objects/data_containers.py
+++ b/yt/data_objects/data_containers.py
@@ -419,7 +419,7 @@ def _parameter_iterate(self, seq):
     def write_out(self, filename, fields=None, format="%0.16e"):
         if fields is None: fields=sorted(self.field_data.keys())
         if self._key_fields is None: raise ValueError
-        field_order = self._key_fields[:]
+        field_order = sorted(self._determine_fields(self._key_fields))
         for field in field_order: self[field]
         field_order += [field for field in fields if field not in field_order]
         fid = open(filename,"w")
diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index 382afe66e4c..36eb467c527 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -48,9 +48,10 @@ def test_write_out():
         file_row_1 = file.readline()
         file_row_2 = file.readline()
         file_row_2 = np.array(file_row_2.split('\t'), dtype=np.float64)
-    _keys = [str(k) for k in sp.field_data.keys()]
+    sorted_keys = sorted(sp.field_data.keys())
+    _keys = [str(k) for k in sorted_keys]
     _keys = "\t".join(["#"] + _keys + ["\n"])
-    _data = [sp.field_data[k][0] for k in sp.field_data.keys()]
+    _data = [sp.field_data[k][0] for k in sorted_keys]
 
     assert_equal(_keys, file_row_1)
     assert_array_equal(_data, file_row_2)
@@ -67,12 +68,16 @@ def test_save_object():
     sp.save_object("my_sphere_2")
 
 def test_to_dataframe():
-    fields = ["density", "velocity_z"]
-    ds = fake_random_ds(6)
-    dd = ds.all_data()
-    df1 = dd.to_dataframe(fields)
-    assert_array_equal(dd[fields[0]], df1[fields[0]])
-    assert_array_equal(dd[fields[1]], df1[fields[1]])
+    try:
+        import pandas as pd
+        fields = ["density", "velocity_z"]
+        ds = fake_random_ds(6)
+        dd = ds.all_data()
+        df1 = dd.to_dataframe(fields)
+        assert_array_equal(dd[fields[0]], df1[fields[0]])
+        assert_array_equal(dd[fields[1]], df1[fields[1]])
+    except ImportError:
+        pass
 
 def test_std():
     ds = fake_random_ds(3)

From 1550eab59930afbd44fdf20c1fe729dfd9127dc1 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 20:18:48 -0400
Subject: [PATCH 08/15] fixed pandas import flake8 error

---
 yt/data_objects/tests/test_data_containers.py | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index 36eb467c527..ceece1fd19c 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -69,13 +69,15 @@ def test_save_object():
 
 def test_to_dataframe():
     try:
-        import pandas as pd
-        fields = ["density", "velocity_z"]
-        ds = fake_random_ds(6)
-        dd = ds.all_data()
-        df1 = dd.to_dataframe(fields)
-        assert_array_equal(dd[fields[0]], df1[fields[0]])
-        assert_array_equal(dd[fields[1]], df1[fields[1]])
+        import importlib
+        pandas_loader = importlib.util.find_spec("pandas")
+        if pandas_loader is not None:
+            fields = ["density", "velocity_z"]
+            ds = fake_random_ds(6)
+            dd = ds.all_data()
+            df1 = dd.to_dataframe(fields)
+            assert_array_equal(dd[fields[0]], df1[fields[0]])
+            assert_array_equal(dd[fields[1]], df1[fields[1]])
     except ImportError:
         pass
 

From 11f62ca633a12e1c96eaf99865c4932a92d6eb56 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 21:35:02 -0400
Subject: [PATCH 09/15] closing file explicitly due to py2 with context mgr

---
 yt/data_objects/tests/test_data_containers.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index ceece1fd19c..d0b99cba9f1 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -64,6 +64,7 @@ def test_save_object():
         loaded_sphere = obj["my_sphere_1"][1]
     assert_array_equal(loaded_sphere.center, sp.center)
     assert_equal(loaded_sphere.radius, sp.radius)
+    obj.close()
 
     sp.save_object("my_sphere_2")
 

From 77c27d52ff15696f09df9eea071d83456427a637 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 11 Jun 2018 23:47:23 -0400
Subject: [PATCH 10/15] Removed context mgr usage from test

---
 yt/data_objects/tests/test_data_containers.py | 4 ++--
 yt/utilities/input_validator.py               | 0
 yt/utilities/tests/test_input_validator.py    | 0
 3 files changed, 2 insertions(+), 2 deletions(-)
 create mode 100644 yt/utilities/input_validator.py
 create mode 100644 yt/utilities/tests/test_input_validator.py

diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index d0b99cba9f1..a7d0c825d9b 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -60,8 +60,8 @@ def test_save_object():
     ds = fake_particle_ds()
     sp = ds.sphere(ds.domain_center, 0.25)
     sp.save_object("my_sphere_1", filename="test_save_obj")
-    with shelve.open("test_save_obj", protocol=-1) as obj:
-        loaded_sphere = obj["my_sphere_1"][1]
+    obj = shelve.open("test_save_obj", protocol=-1)
+    loaded_sphere = obj["my_sphere_1"][1]
     assert_array_equal(loaded_sphere.center, sp.center)
     assert_equal(loaded_sphere.radius, sp.radius)
     obj.close()
diff --git a/yt/utilities/input_validator.py b/yt/utilities/input_validator.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/yt/utilities/tests/test_input_validator.py b/yt/utilities/tests/test_input_validator.py
new file mode 100644
index 00000000000..e69de29bb2d

From 9abeca028086b6f60c5cb66cdf64fef156aeb60e Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Tue, 12 Jun 2018 02:53:57 -0400
Subject: [PATCH 11/15] fixed incompatibility b/w py 2 and 3

---
 yt/data_objects/tests/test_data_containers.py | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index a7d0c825d9b..2a7d0bcd894 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -70,15 +70,14 @@ def test_save_object():
 
 def test_to_dataframe():
     try:
-        import importlib
-        pandas_loader = importlib.util.find_spec("pandas")
-        if pandas_loader is not None:
-            fields = ["density", "velocity_z"]
-            ds = fake_random_ds(6)
-            dd = ds.all_data()
-            df1 = dd.to_dataframe(fields)
-            assert_array_equal(dd[fields[0]], df1[fields[0]])
-            assert_array_equal(dd[fields[1]], df1[fields[1]])
+        import pandas as pd
+        pd # to ignore Flake8 error
+        fields = ["density", "velocity_z"]
+        ds = fake_random_ds(6)
+        dd = ds.all_data()
+        df1 = dd.to_dataframe(fields)
+        assert_array_equal(dd[fields[0]], df1[fields[0]])
+        assert_array_equal(dd[fields[1]], df1[fields[1]])
     except ImportError:
         pass
 

From 70682e52ae2a4895bb39497150074ef53bfa2bf5 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Thu, 14 Jun 2018 00:58:37 -0400
Subject: [PATCH 12/15] Updated as per first code review comments

---
 .travis.yml                                   |   3 +-
 appveyor.yml                                  |   2 +-
 .../construction_data_containers.py           |   3 +-
 yt/data_objects/data_containers.py            |  95 +++++++++++------
 yt/data_objects/tests/test_data_containers.py | 100 +++++++++---------
 yt/utilities/input_validator.py               |   0
 yt/utilities/tests/test_input_validator.py    |   0
 7 files changed, 118 insertions(+), 85 deletions(-)
 delete mode 100644 yt/utilities/input_validator.py
 delete mode 100644 yt/utilities/tests/test_input_validator.py

diff --git a/.travis.yml b/.travis.yml
index 488619283b0..caec2064af5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,6 +23,7 @@ env:
     FLAKE8=flake8
     CODECOV=codecov
     COVERAGE=coverage
+    PANDAS=pandas
 
 before_install:
   - |
@@ -50,7 +51,7 @@ install:
     pip install --upgrade wheel
     pip install --upgrade setuptools
     # Install dependencies
-    pip install mock $NUMPY $SCIPY $H5PY $CYTHON $MATPLOTLIB $SYMPY $FASTCACHE $IPYTHON $FLAKE8 $CODECOV $COVERAGE nose nose-timer
+    pip install mock $NUMPY $SCIPY $H5PY $CYTHON $MATPLOTLIB $SYMPY $FASTCACHE $IPYTHON $FLAKE8 $CODECOV $COVERAGE $PANDAS nose nose-timer
     # install yt
     pip install -e .
 
diff --git a/appveyor.yml b/appveyor.yml
index 6b888d503ce..5671182a393 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -29,7 +29,7 @@ install:
     - "python --version"
 
     # Install specified version of numpy and dependencies
-    - "conda install --yes -c conda-forge numpy scipy nose setuptools ipython Cython sympy fastcache h5py matplotlib flake8 mock"
+    - "conda install --yes -c conda-forge numpy scipy nose setuptools ipython Cython sympy fastcache h5py matplotlib flake8 mock pandas"
     - "pip install -e ."
 
 # Not a .NET project
diff --git a/yt/data_objects/construction_data_containers.py b/yt/data_objects/construction_data_containers.py
index 135fb6942be..41a02da3149 100644
--- a/yt/data_objects/construction_data_containers.py
+++ b/yt/data_objects/construction_data_containers.py
@@ -923,7 +923,8 @@ def __init__(self, *args, **kwargs):
 
     def _setup_data_source(self, level_state = None):
         if level_state is None:
-            return super(YTSmoothedCoveringGrid, self)._setup_data_source()
+            super(YTSmoothedCoveringGrid, self)._setup_data_source()
+            return
         # We need a buffer region to allow for zones that contribute to the
         # interpolation but are not directly inside our bounds
         level_state.data_source = self.ds.region(
diff --git a/yt/data_objects/data_containers.py b/yt/data_objects/data_containers.py
index d0c8d5d295a..3764fa846d8 100644
--- a/yt/data_objects/data_containers.py
+++ b/yt/data_objects/data_containers.py
@@ -32,7 +32,7 @@
     mylog, \
     ensure_list, \
     fix_axis, \
-    iterable
+    iterable, validate_width_tuple
 from yt.units.unit_object import UnitParseError
 from yt.units.yt_array import \
     YTArray, \
@@ -50,7 +50,7 @@
     YTDataSelectorNotImplemented, \
     YTDimensionalityError, \
     YTBooleanObjectError, \
-    YTBooleanObjectsWrongDataset
+    YTBooleanObjectsWrongDataset, YTException
 from yt.utilities.lib.marching_cubes import \
     march_cubes_grid, march_cubes_grid_flux
 from yt.utilities.parallel_tools.parallel_analysis_interface import \
@@ -71,15 +71,6 @@
 
 data_object_registry = {}
 
-def force_array(item, shape):
-    try:
-        return item.copy()
-    except AttributeError:
-        if item:
-            return np.ones(shape, dtype='bool')
-        else:
-            return np.zeros(shape, dtype='bool')
-
 def sanitize_weight_field(ds, field, weight):
     field_object = ds._get_field_info(field)
     if weight is None:
@@ -232,13 +223,6 @@ def has_field_parameter(self, name):
         """
         return name in self.field_parameters
 
-    def convert(self, datatype):
-        """
-        This will attempt to convert a given unit to cgs from code units.
-        It either returns the multiplicative factor or throws a KeyError.
-        """
-        return self.ds[datatype]
-
     def clear_data(self):
         """
         Clears out all data from the YTDataContainer instance, freeing memory.
@@ -417,21 +401,73 @@ def _parameter_iterate(self, seq):
 
     _key_fields = None
     def write_out(self, filename, fields=None, format="%0.16e"):
-        if fields is None: fields=sorted(self.field_data.keys())
-        if self._key_fields is None: raise ValueError
-        field_order = sorted(self._determine_fields(self._key_fields))
+        """Write out the YTDataContainer object in a text file.
+
+        This function will take a data object and produce a tab delimited text
+        file containing the fields presently existing and the fields given in
+        the ``fields`` list.
+
+        Parameters
+        ----------
+        filename : String
+            The name of the file to write to.
+
+        fields : List of string, Default = None
+            If this is supplied, these fields will be added to the list of
+            fields to be saved to disk. If not supplied, whatever fields
+            presently exist will be used.
+
+        format : String, Default = "%0.16e"
+            Format of numbers to be written in the file.
+
+        Raises
+        ------
+        ValueError
+            Raised when there is no existing field.
+
+        YTException
+            Raised when field_type of supplied fields is inconsistent with the
+            field_type of existing fields.
+
+        Examples
+        --------
+        >>> ds = fake_particle_ds()
+        >>> sp = ds.sphere(ds.domain_center, 0.25)
+        >>> sp.write_out("sphere_1.txt")
+        >>> sp.write_out("sphere_2.txt", fields=["cell_volume"])
+        """
+        if fields is None:
+            fields = sorted(self.field_data.keys())
+
+        if self._key_fields is None:
+            raise ValueError
+
+        field_order = self._key_fields
+        diff_fields = [field for field in fields if field not in field_order]
+        field_order += diff_fields
+        field_order = sorted(self._determine_fields(field_order))
+        field_types = {u for u, v in field_order}
+
+        if len(field_types) != 1:
+            diff_fields = self._determine_fields(diff_fields)
+            req_ftype = self._determine_fields(self._key_fields[0])[0][0]
+            f_type = {f for f in diff_fields if f[0] != req_ftype }
+            msg = ("Field type %s of the supplied field %s is inconsistent"
+                   " with field type '%s'." %
+                   ([f[0] for f in f_type], [f[1] for f in f_type], req_ftype))
+            raise YTException(msg)
+
         for field in field_order: self[field]
-        field_order += [field for field in fields if field not in field_order]
-        fid = open(filename,"w")
+        fid = open(filename, "w")
         field_header = [str(f) for f in field_order]
         fid.write("\t".join(["#"] + field_header + ["\n"]))
         field_data = np.array([self.field_data[field] for field in field_order])
         for line in range(field_data.shape[1]):
-            field_data[:,line].tofile(fid, sep="\t", format=format)
+            field_data[:, line].tofile(fid, sep="\t", format=format)
             fid.write("\n")
         fid.close()
 
-    def save_object(self, name, filename = None):
+    def save_object(self, name, filename=None):
         """
         Save an object.  If *filename* is supplied, it will be stored in
         a :mod:`shelve` file of that name.  Otherwise, it will be stored via
@@ -446,7 +482,7 @@ def save_object(self, name, filename = None):
         else:
             self.index.save_object(self, name)
 
-    def to_dataframe(self, fields = None):
+    def to_dataframe(self, fields=None):
         r"""Export a data object to a pandas DataFrame.
 
         This function will take a data object and construct from it and
@@ -1664,12 +1700,9 @@ def to_frb(self, width, resolution, center=None, height=None,
                     "Currently we only support images centered at R=0. " +
                     "We plan to generalize this in the near future")
             from yt.visualization.fixed_resolution import CylindricalFixedResolutionBuffer
-            if isinstance(width, tuple):
-               radius = width[0]
-            else:
-                radius = width
+            validate_width_tuple(width)
             if iterable(resolution): resolution = max(resolution)
-            frb = CylindricalFixedResolutionBuffer(self, radius, resolution)
+            frb = CylindricalFixedResolutionBuffer(self, width, resolution)
             return frb
 
         if center is None:
diff --git a/yt/data_objects/tests/test_data_containers.py b/yt/data_objects/tests/test_data_containers.py
index 2a7d0bcd894..2a887d8f634 100644
--- a/yt/data_objects/tests/test_data_containers.py
+++ b/yt/data_objects/tests/test_data_containers.py
@@ -5,16 +5,16 @@
 from numpy.testing import assert_array_equal
 
 from yt.data_objects.data_containers import YTDataContainer
-from yt.testing import assert_equal, fake_random_ds, fake_amr_ds, fake_particle_ds
-from yt.utilities.exceptions import YTFieldNotFound
-
+from yt.testing import assert_equal, fake_random_ds, fake_amr_ds,\
+    fake_particle_ds, requires_module
+from yt.utilities.exceptions import YTFieldNotFound, YTException
 
 def test_yt_data_container():
     # Test if ds could be None
     with assert_raises(RuntimeError) as err:
         YTDataContainer(None, None)
-    desired = 'Error: ds must be set either through class type or parameter' \
-              ' to the constructor'
+    desired = ('Error: ds must be set either through class'
+               ' type or parameter to the constructor')
     assert_equal(str(err.exception), desired)
 
     # Test if field_data key exists
@@ -24,37 +24,41 @@ def test_yt_data_container():
     assert_equal('pz' in proj.keys(), False)
 
     # Delete the key and check if exits
-    proj.__delitem__('px')
+    del proj['px']
     assert_equal('px' in proj.keys(), False)
-    proj.__delitem__('density')
+    del proj['density']
     assert_equal('density' in proj.keys(), False)
 
     # Delete a non-existent field
     with assert_raises(YTFieldNotFound) as ex:
-        proj.__delitem__('p_mass')
+        del proj['p_mass']
     desired = "Could not find field '('stream', 'p_mass')' in UniformGridData."
     assert_equal(str(ex.exception), desired)
 
-    # Test the convert method
-    assert_equal(proj.convert('HydroMethod'), -1)
-
 def test_write_out():
     filename = "sphere.txt"
     ds = fake_particle_ds()
     sp = ds.sphere(ds.domain_center, 0.25)
-    sp.write_out(filename)
+    sp.write_out(filename, fields=["cell_volume"])
 
     with open(filename, "r") as file:
         file_row_1 = file.readline()
         file_row_2 = file.readline()
         file_row_2 = np.array(file_row_2.split('\t'), dtype=np.float64)
     sorted_keys = sorted(sp.field_data.keys())
-    _keys = [str(k) for k in sorted_keys]
-    _keys = "\t".join(["#"] + _keys + ["\n"])
-    _data = [sp.field_data[k][0] for k in sorted_keys]
+    keys = [str(k) for k in sorted_keys]
+    keys = "\t".join(["#"] + keys + ["\n"])
+    data = [sp.field_data[k][0] for k in sorted_keys]
+
+    assert_equal(keys, file_row_1)
+    assert_array_equal(data, file_row_2)
 
-    assert_equal(_keys, file_row_1)
-    assert_array_equal(_data, file_row_2)
+    # Test for exception
+    with assert_raises(YTException) as ex:
+        sp.write_out(filename, fields=["particle_position_x"])
+    desired = ("Field type ['all'] of the supplied field ['particle_position_x']"
+               " is in consistent with field type 'gas'.")
+    assert_equal(str(ex.exception)[:50], desired[:50])
 
 def test_save_object():
     ds = fake_particle_ds()
@@ -62,60 +66,54 @@ def test_save_object():
     sp.save_object("my_sphere_1", filename="test_save_obj")
     obj = shelve.open("test_save_obj", protocol=-1)
     loaded_sphere = obj["my_sphere_1"][1]
+    obj.close()
     assert_array_equal(loaded_sphere.center, sp.center)
     assert_equal(loaded_sphere.radius, sp.radius)
-    obj.close()
+    for k in loaded_sphere._key_fields:
+        assert_array_equal(loaded_sphere[k], sp[k])
 
-    sp.save_object("my_sphere_2")
+    # Object is saved but retrieval is not working
+    # sp.save_object("my_sphere_2")
+    # loaded_sphere = ds.index.load_object("my_sphere_2")
+    # for k in loaded_sphere._key_fields:
+    #     assert_array_equal(loaded_sphere[k], sp[k])
 
+@requires_module("pandas")
 def test_to_dataframe():
-    try:
-        import pandas as pd
-        pd # to ignore Flake8 error
-        fields = ["density", "velocity_z"]
-        ds = fake_random_ds(6)
-        dd = ds.all_data()
-        df1 = dd.to_dataframe(fields)
-        assert_array_equal(dd[fields[0]], df1[fields[0]])
-        assert_array_equal(dd[fields[1]], df1[fields[1]])
-    except ImportError:
-        pass
+    fields = ["density", "velocity_z"]
+    ds = fake_random_ds(6)
+    dd = ds.all_data()
+    df1 = dd.to_dataframe(fields)
+    assert_array_equal(dd[fields[0]], df1[fields[0]])
+    assert_array_equal(dd[fields[1]], df1[fields[1]])
 
 def test_std():
     ds = fake_random_ds(3)
     ds.all_data().std('density', weight="velocity_z")
 
 def test_to_frb():
-    ds = fake_amr_ds(fields=["density", "cell_mass"], geometry="cylindrical",
-                     particles=16**3)
-    proj = ds.proj("density", weight_field="cell_mass", axis=1,
-                   data_source=ds.all_data())
-    proj.to_frb((1.0, 'unitary'), 64)
+    # Test cylindrical geometry
+    fields = ["density", "cell_mass"]
+    ds = fake_amr_ds(fields=fields, geometry="cylindrical", particles=16**3)
+    dd = ds.all_data()
+    proj = ds.proj("density", weight_field="cell_mass", axis=1, data_source=dd)
+    frb = proj.to_frb((1.0, 'unitary'), 64)
+    assert_equal(frb.radius, (1.0, 'unitary'))
+    assert_equal(frb.buff_size, 64)
 
 def test_extract_isocontours():
     # Test isocontour properties for AMRGridData
     ds = fake_amr_ds(fields=["density", "cell_mass"], particles=16**3)
     dd = ds.all_data()
-    rho = dd.quantities["WeightedAverageQuantity"]("density",
-                                                   weight="cell_mass")
+    q = dd.quantities["WeightedAverageQuantity"]
+    rho = q("density", weight="cell_mass")
     dd.extract_isocontours("density", rho, "triangles.obj", True)
-    dd.calculate_isocontour_flux("density", rho, "x", "y", "z",
-                                 "dx")
+    dd.calculate_isocontour_flux("density", rho, "x", "y", "z", "dx")
 
     # Test error in case of ParticleData
     ds = fake_particle_ds()
     dd = ds.all_data()
-    rho = dd.quantities["WeightedAverageQuantity"]("particle_velocity_x",
-                                                   weight="particle_mass")
+    q = dd.quantities["WeightedAverageQuantity"]
+    rho = q("particle_velocity_x", weight="particle_mass")
     with assert_raises(NotImplementedError):
         dd.extract_isocontours("density", rho, sample_values='x')
-
-def test_extract_connected_sets():
-
-    ds = fake_random_ds(16, nprocs=8, particles=16 ** 3)
-    data_source = ds.disk([0.5, 0.5, 0.5], [0., 0., 1.], (8, 'kpc'), (1, 'kpc'))
-    field = ("gas", "density")
-    min_val, max_val = data_source[field].min() / 2, data_source[field].max() / 2
-
-    data_source.extract_connected_sets(field, 3, min_val, max_val,
-                                              log_space=True, cumulative=True)
diff --git a/yt/utilities/input_validator.py b/yt/utilities/input_validator.py
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/yt/utilities/tests/test_input_validator.py b/yt/utilities/tests/test_input_validator.py
deleted file mode 100644
index e69de29bb2d..00000000000

From cb3bf7185978cf1fd38e9745e838234f820e4d0e Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Thu, 14 Jun 2018 02:23:37 -0400
Subject: [PATCH 13/15] Resolved  pandas dependency issue

---
 .travis.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index caec2064af5..55b69685fd3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,7 +23,7 @@ env:
     FLAKE8=flake8
     CODECOV=codecov
     COVERAGE=coverage
-    PANDAS=pandas
+    PANDAS=pandas<0.21
 
 before_install:
   - |
@@ -59,7 +59,7 @@ jobs:
   include:
     - stage: lint
       python: 3.4
-      env: NUMPY=numpy==1.10.4 CYTHON=cython==0.24 MATPLOTLIB= SYMPY= H5PY= SCIPY= FASTCACHE= IPYTHON=
+      env: NUMPY=numpy==1.10.4 CYTHON=cython==0.24 MATPLOTLIB= SYMPY= H5PY= SCIPY= FASTCACHE= IPYTHON= PANDAS=
       script: flake8 yt/
 
     - stage: tests

From 4f8fb5dac6480d47d56c920bbbb6dc1a624eb7d9 Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Thu, 14 Jun 2018 14:51:13 -0400
Subject: [PATCH 14/15] Updated Lint stage to run in py3.6; pinned pandas for
 py3.4

---
 .travis.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 55b69685fd3..97cd65dc20b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,7 +23,7 @@ env:
     FLAKE8=flake8
     CODECOV=codecov
     COVERAGE=coverage
-    PANDAS=pandas<0.21
+    PANDAS=pandas
 
 before_install:
   - |
@@ -58,7 +58,7 @@ install:
 jobs:
   include:
     - stage: lint
-      python: 3.4
+      python: 3.6
       env: NUMPY=numpy==1.10.4 CYTHON=cython==0.24 MATPLOTLIB= SYMPY= H5PY= SCIPY= FASTCACHE= IPYTHON= PANDAS=
       script: flake8 yt/
 
@@ -74,7 +74,7 @@ jobs:
 
     - stage: tests
       python: 3.4
-      env: FLAKE8=
+      env: FLAKE8= PANDAS=pandas==0.20
       script: coverage run $(which nosetests) -c nose.cfg yt
 
     - stage: tests

From d12ca6e1033c61c2c2c4fa7a443f5e74d4b5b30e Mon Sep 17 00:00:00 2001
From: git-abhishek <36498066+git-abhishek@users.noreply.github.com>
Date: Mon, 18 Jun 2018 16:26:58 -0400
Subject: [PATCH 15/15] using with statement for file write ops

---
 yt/data_objects/data_containers.py | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/yt/data_objects/data_containers.py b/yt/data_objects/data_containers.py
index 3764fa846d8..f503fc16602 100644
--- a/yt/data_objects/data_containers.py
+++ b/yt/data_objects/data_containers.py
@@ -458,14 +458,13 @@ def write_out(self, filename, fields=None, format="%0.16e"):
             raise YTException(msg)
 
         for field in field_order: self[field]
-        fid = open(filename, "w")
-        field_header = [str(f) for f in field_order]
-        fid.write("\t".join(["#"] + field_header + ["\n"]))
-        field_data = np.array([self.field_data[field] for field in field_order])
-        for line in range(field_data.shape[1]):
-            field_data[:, line].tofile(fid, sep="\t", format=format)
-            fid.write("\n")
-        fid.close()
+        with open(filename, "w") as fid:
+            field_header = [str(f) for f in field_order]
+            fid.write("\t".join(["#"] + field_header + ["\n"]))
+            field_data = np.array([self.field_data[field] for field in field_order])
+            for line in range(field_data.shape[1]):
+                field_data[:, line].tofile(fid, sep="\t", format=format)
+                fid.write("\n")
 
     def save_object(self, name, filename=None):
         """