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ENH: overwrite keyword in DataFrame.update #1478

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ENH: overwrite keyword in DataFrame.update #1478

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3d8df3a
ENH: overwrite keyword in DataFrame.update
Jun 15, 2012
8130f09
ENH: filter_func keyword to DataFrame.update, related to #1477
Jun 15, 2012
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16 changes: 14 additions & 2 deletions pandas/core/frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3143,7 +3143,7 @@ def combine_first(self, other):
combiner = lambda x, y: np.where(isnull(x), y, x)
return self.combine(other, combiner)

def update(self, other, join='left'):
def update(self, other, join='left', overwrite=True, filter_func=None):
"""
Modify DataFrame in place using non-NA values from passed
DataFrame. Aligns on indices
Expand All @@ -3152,6 +3152,11 @@ def update(self, other, join='left'):
----------
other : DataFrame
join : {'left', 'right', 'outer', 'inner'}, default 'left'
overwrite : boolean, default True
If True then overwrite values for common keys in the calling frame
filter_func : callable(1d-array) -> 1d-array<boolean>, default None
Can choose to replace values other than NA. Return True for values
that should be updated
"""
if join != 'left':
raise NotImplementedError
Expand All @@ -3160,7 +3165,14 @@ def update(self, other, join='left'):
for col in self.columns:
this = self[col].values
that = other[col].values
self[col] = np.where(isnull(that), this, that)
if filter_func is not None:
mask = -filter_func(this) | isnull(that)
else:
if overwrite:
mask = isnull(that)
else:
mask = notnull(this)
self[col] = np.where(mask, this, that)

#----------------------------------------------------------------------
# Misc methods
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35 changes: 35 additions & 0 deletions pandas/tests/test_frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5235,6 +5235,41 @@ def test_update(self):
[1.5, nan, 7.]])
assert_frame_equal(df, expected)

def test_update_nooverwrite(self):
df = DataFrame([[1.5, nan, 3.],
[1.5, nan, 3.],
[1.5, nan, 3],
[1.5, nan, 3]])

other = DataFrame([[3.6, 2., np.nan],
[np.nan, np.nan, 7]], index=[1, 3])

df.update(other, overwrite=False)

expected = DataFrame([[1.5, nan, 3],
[1.5, 2, 3],
[1.5, nan, 3],
[1.5, nan, 3.]])
assert_frame_equal(df, expected)

def test_update_filtered(self):
df = DataFrame([[1.5, nan, 3.],
[1.5, nan, 3.],
[1.5, nan, 3],
[1.5, nan, 3]])

other = DataFrame([[3.6, 2., np.nan],
[np.nan, np.nan, 7]], index=[1, 3])

df.update(other, filter_func=lambda x: x > 2)

expected = DataFrame([[1.5, nan, 3],
[1.5, nan, 3],
[1.5, nan, 3],
[1.5, nan, 7.]])
assert_frame_equal(df, expected)


def test_combineAdd(self):
# trivial
comb = self.frame.combineAdd(self.frame)
Expand Down