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REF: repr - allow block to override values that get formatted #17143

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Aug 4, 2017
Merged

REF: repr - allow block to override values that get formatted #17143

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f6e376f
REF: repr - allow block to override values that get formatted
jorisvandenbossche Aug 1, 2017
ec7ff5d
extra redirect + move tests
jorisvandenbossche Aug 2, 2017
7e259c9
add to setup.py + specify int64 in test
jorisvandenbossche Aug 2, 2017
000c6fc
Merge remote-tracking branch 'upstream/master' into internals-formatt…
jorisvandenbossche Aug 2, 2017
dcd3c0f
remove usage of fastpath in test example
jorisvandenbossche Aug 3, 2017
b41b713
pep8
jorisvandenbossche Aug 3, 2017
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8 changes: 8 additions & 0 deletions pandas/core/internals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -159,6 +159,10 @@ def internal_values(self, dtype=None):
"""
return self.values

def formatting_values(self):
"""Return the internal values used by the DataFrame/SeriesFormatter"""
return self.internal_values()

def get_values(self, dtype=None):
"""
return an internal format, currently just the ndarray
Expand Down Expand Up @@ -4316,6 +4320,10 @@ def external_values(self):
def internal_values(self):
return self._block.internal_values()

def formatting_values(self):
"""Return the internal values used by the DataFrame/SeriesFormatter"""
return self._block.formatting_values()

def get_values(self):
""" return a dense type view """
return np.array(self._block.to_dense(), copy=False)
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6 changes: 6 additions & 0 deletions pandas/core/series.py
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Original file line number Diff line number Diff line change
Expand Up @@ -398,6 +398,12 @@ def _values(self):
""" return the internal repr of this data """
return self._data.internal_values()

def _formatting_values(self):
"""Return the values that can be formatted (used by SeriesFormatter
and DataFrameFormatter)
"""
return self._data.formatting_values()

def get_values(self):
""" same as values (but handles sparseness conversions); is a view """
return self._data.get_values()
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6 changes: 4 additions & 2 deletions pandas/io/formats/format.py
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Expand Up @@ -237,7 +237,8 @@ def _get_formatted_index(self):
return fmt_index, have_header

def _get_formatted_values(self):
return format_array(self.tr_series._values, None,
values_to_format = self.tr_series._formatting_values()
return format_array(values_to_format, None,
float_format=self.float_format, na_rep=self.na_rep)

def to_string(self):
Expand Down Expand Up @@ -694,7 +695,8 @@ def to_latex(self, column_format=None, longtable=False, encoding=None,
def _format_col(self, i):
frame = self.tr_frame
formatter = self._get_formatter(i)
return format_array(frame.iloc[:, i]._values, formatter,
values_to_format = frame.iloc[:, i]._formatting_values()
return format_array(values_to_format, formatter,
float_format=self.float_format, na_rep=self.na_rep,
space=self.col_space, decimal=self.decimal)

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Empty file added pandas/tests/internals/__init__.py
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29 changes: 29 additions & 0 deletions pandas/tests/internals/test_external_block.py
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@@ -0,0 +1,29 @@
# -*- coding: utf-8 -*-
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need to add this in setup.py as well

# pylint: disable=W0102

import numpy as np

import pandas as pd
from pandas.core.internals import Block, BlockManager, SingleBlockManager


class CustomBlock(Block):

def formatting_values(self):
return np.array(["Val: {}".format(i) for i in self.values])


def test_custom_repr():
values = np.arange(3, dtype='int64')

# series
block = CustomBlock(values, placement=slice(0, 3))
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I wouldn't pass fastpath, that's not really a public option.

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If you don't use fastpath, it does not preserve the Block type. Eg:

In [53]: block = CustomBlock(values, placement=slice(0, 3))

In [54]: s = pd.Series(block, index=pd.RangeIndex(3), fastpath=True)

In [55]: s._data._block
Out[55]: CustomBlock: 3 dtype: int64

In [56]: s = pd.Series(block, index=pd.RangeIndex(3))

In [57]: s._data._block
Out[57]: ObjectBlock: 3 dtype: object

The reason is that we don't check for isinstance(data, Block) in the Series __init__.py (we do for isinstance(data, SingleBlockManager) in the non-fastpath code path.

For that reason I am also using the fastpath in GeoPandas.

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hmm, that looks like a bug. if you change that does it break anything else? (could be followup as well)

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In general it has proven a bit difficult to construct Series and DataFrame objects from given blocks, without re-creating the blocks (eg in Series, the block gets converted to array, which is then passed to SingleBlockManager, which does not preserve the block type)

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you generally need to give it a SingleBkockManger or BlockManager

blocks are a lower level item
and Series/DataFrame don't/shouldn't know about these

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yes, that's fine. But slightly change my comment: it has also proven to be difficult to add a block to a BlockManager with preserving the block type.

Once we have a BlockManager, it's indeed simply passing it to DataFrame(..) to get a df. That's what we do to create dataframes, I should probably take the same approach to create SingleBlockManager for the series case instead of using that fastpath.

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why is it hard to add a Block to BM
something is wrong if it's hard

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you have Block.set and Block.insert methods to add things to a Block, but those also do not preserve the block you pass

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See here for a work around that I now use in the geopandas refactor branch: geopandas/geopandas#467 (comment)
Basically it is constructing a dataframe, taking the blocks and axes out of it, append a Block to the blocks, and a value to the column axis, and create a new Block from those.

(but given the length of code in Block.insert/set, this is maybe actually a simple way)

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BTW, I added a commit with an attempt to remove the usage of fastpath


s = pd.Series(SingleBlockManager(block, pd.RangeIndex(3)))
assert repr(s) == '0 Val: 0\n1 Val: 1\n2 Val: 2\ndtype: int64'

# dataframe
block = CustomBlock(values.reshape(1, -1), placement=slice(0, 1))
blk_mgr = BlockManager([block], [['col'], range(3)])
df = pd.DataFrame(blk_mgr)
assert repr(df) == ' col\n0 Val: 0\n1 Val: 1\n2 Val: 2'
0 pandas/tests/test_internals.py → pandas/tests/internals/test_internals.py
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1 change: 1 addition & 0 deletions setup.py
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Expand Up @@ -670,6 +670,7 @@ def pxd(name):
'pandas.tests.indexes.datetimes',
'pandas.tests.indexes.timedeltas',
'pandas.tests.indexes.period',
'pandas.tests.internals',
'pandas.tests.io',
'pandas.tests.io.json',
'pandas.tests.io.parser',
Expand Down