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Copy on write using weakrefs (part 2) #12036

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Copy on write using weakrefs (part 2) #12036

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85a7ac1
first pass at fixing
Dec 16, 2015
b0cff8a
fixed iloc issue
Dec 16, 2015
d146857
works except for settingoncopy warning, which is now broken
Jan 13, 2016
01f66a2
Basic working implementation
Sep 30, 2015
fcfc6c5
now keeps columns as views
Oct 30, 2015
c77ed4d
check for dead weakrefs
Nov 1, 2015
8e72c66
store children in weakValueDictionary instead of list
Nov 2, 2015
00869ca
Remove redundant copying
Nov 2, 2015
9085bea
Add back reference to origin df to protect against broken chains of v…
Nov 3, 2015
a5f64fc
make _is_view more conservative on multi-block objects
Nov 4, 2015
a64af02
fix multi-index behavior
Dec 4, 2015
6a06d87
fix test_merge
Dec 4, 2015
20e8192
update add_to_child to register_new_child
Dec 10, 2015
2ff12a9
modify dataframe constructor
Dec 10, 2015
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Add back reference to origin df to protect against broken chains of v… 
…iews
  • Loading branch information
Nick Eubank committed Jan 13, 2016
commit 9085bea774f358eb4e3fe72b90610820eff42b6c
9 changes: 7 additions & 2 deletions pandas/core/generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,7 @@ class NDFrame(PandasObject):
'is_copy', '_subtyp', '_index',
'_default_kind', '_default_fill_value', '_metadata',
'__array_struct__', '__array_interface__', '_children',
'_is_column_view']
'_is_column_view', '_original_parent']
_internal_names_set = set(_internal_names)
_accessors = frozenset([])
_metadata = []
Expand All @@ -108,6 +108,7 @@ def __init__(self, data, axes=None, copy=False, dtype=None,
object.__setattr__(self, '_item_cache', {})
object.__setattr__(self, '_children', weakref.WeakValueDictionary())
object.__setattr__(self, '_is_column_view', False)
object.__setattr__(self, '_original_parent', weakref.WeakValueDictionary())


def _validate_dtype(self, dtype):
Expand Down Expand Up @@ -1244,7 +1245,11 @@ def _execute_copy_on_write(self):
def _add_to_children(self, view_to_append):
self._children[id(view_to_append)] = view_to_append


if len(self._original_parent) is 0:
view_to_append._original_parent['parent'] = self
else:
self._original_parent['parent']._add_to_children(view_to_append)

def __delitem__(self, key):
"""
Delete item
Expand Down
17 changes: 17 additions & 0 deletions pandas/tests/test_generic.py
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Expand Up @@ -1808,6 +1808,23 @@ def test_copy_on_write(self):
self.assertTrue(v.loc[0] == -88)
self.assertTrue(v._is_view)

###
# Make sure that no problems if view created on view and middle-view
# gets deleted
#
df = pd.DataFrame({'col1':[1,2], 'col2':[3,4]})
v1 = df.loc[0:0,]
self.assertTrue(len(df._children)==1)

v2 = v1.loc[0:0,]
v2_copy = v2.copy()
self.assertTrue(len(df._children)==2)

del v1

df.loc[0:0, 'col1'] = -88

tm.assert_frame_equal(v2, v2_copy)



Expand Down