"""
concat routines
"""
import numpy as np
import pandas.core.dtypes.concat as _concat
from pandas import DataFrame, Index, MultiIndex, Series, compat
from pandas.core import common as com
from pandas.core.arrays.categorical import (
_factorize_from_iterable, _factorize_from_iterables)
from pandas.core.generic import NDFrame
from pandas.core.index import (
_all_indexes_same, _get_consensus_names, _get_objs_combined_axis,
ensure_index)
import pandas.core.indexes.base as ibase
from pandas.core.internals import concatenate_block_managers
# ---------------------------------------------------------------------
# Concatenate DataFrame objects
def concat(objs, axis=0, join='outer', join_axes=None, ignore_index=False,
keys=None, levels=None, names=None, verify_integrity=False,
sort=None, copy=True):
"""
Concatenate pandas objects along a particular axis with optional set logic
along the other axes.
Can also add a layer of hierarchical indexing on the concatenation axis,
which may be useful if the labels are the same (or overlapping) on
the passed axis number.
Parameters
----------
objs : a sequence or mapping of Series, DataFrame, or Panel objects
If a dict is passed, the sorted keys will be used as the `keys`
argument, unless it is passed, in which case the values will be
selected (see below). Any None objects will be dropped silently unless
they are all None in which case a ValueError will be raised
axis : {0/'index', 1/'columns'}, default 0
The axis to concatenate along
join : {'inner', 'outer'}, default 'outer'
How to handle indexes on other axis(es)
join_axes : list of Index objects
Specific indexes to use for the other n - 1 axes instead of performing
inner/outer set logic
ignore_index : boolean, default False
If True, do not use the index values along the concatenation axis. The
resulting axis will be labeled 0, ..., n - 1. This is useful if you are
concatenating objects where the concatenation axis does not have
meaningful indexing information. Note the index values on the other
axes are still respected in the join.
keys : sequence, default None
If multiple levels passed, should contain tuples. Construct
hierarchical index using the passed keys as the outermost level
levels : list of sequences, default None
Specific levels (unique values) to use for constructing a
MultiIndex. Otherwise they will be inferred from the keys
names : list, default None
Names for the levels in the resulting hierarchical index
verify_integrity : boolean, default False
Check whether the new concatenated axis contains duplicates. This can
be very expensive relative to the actual data concatenation
sort : boolean, default None
Sort non-concatenation axis if it is not already aligned when `join`
is 'outer'. The current default of sorting is deprecated and will
change to not-sorting in a future version of pandas.
Explicitly pass ``sort=True`` to silence the warning and sort.
Explicitly pass ``sort=False`` to silence the warning and not sort.
This has no effect when ``join='inner'``, which already preserves
the order of the non-concatenation axis.
.. versionadded:: 0.23.0
copy : boolean, default True
If False, do not copy data unnecessarily
Returns
-------
concatenated : object, type of objs
When concatenating all ``Series`` along the index (axis=0), a
``Series`` is returned. When ``objs`` contains at least one
``DataFrame``, a ``DataFrame`` is returned. When concatenating along
the columns (axis=1), a ``DataFrame`` is returned.
See Also
--------
Series.append
DataFrame.append
DataFrame.join
DataFrame.merge
Notes
-----
The keys, levels, and names arguments are all optional.
A walkthrough of how this method fits in with other tools for combining
pandas objects can be found `here
<http://pandas.pydata.org/pandas-docs/stable/merging.html>`__.
Examples
--------
Combine two ``Series``.
>>> s1 = pd.Series(['a', 'b'])
>>> s2 = pd.Series(['c', 'd'])
>>> pd.concat([s1, s2])
0 a
1 b
0 c
1 d
dtype: object
Clear the existing index and reset it in the result
by setting the ``ignore_index`` option to ``True``.
>>> pd.concat([s1, s2], ignore_index=True)
0 a
1 b
2 c
3 d
dtype: object
Add a hierarchical index at the outermost level of
the data with the ``keys`` option.
>>> pd.concat([s1, s2], keys=['s1', 's2',])
s1 0 a
1 b
s2 0 c
1 d
dtype: object
Label the index keys you create with the ``names`` option.
>>> pd.concat([s1, s2], keys=['s1', 's2'],
... names=['Series name', 'Row ID'])
Series name Row ID
s1 0 a
1 b
s2 0 c
1 d
dtype: object
Combine two ``DataFrame`` objects with identical columns.
>>> df1 = pd.DataFrame([['a', 1], ['b', 2]],
... columns=['letter', 'number'])
>>> df1
letter number
0 a 1
1 b 2
>>> df2 = pd.DataFrame([['c', 3], ['d', 4]],
... columns=['letter', 'number'])
>>> df2
letter number
0 c 3
1 d 4
>>> pd.concat([df1, df2])
letter number
0 a 1
1 b 2
0 c 3
1 d 4
Combine ``DataFrame`` objects with overlapping columns
and return everything. Columns outside the intersection will
be filled with ``NaN`` values.
>>> df3 = pd.DataFrame([['c', 3, 'cat'], ['d', 4, 'dog']],
... columns=['letter', 'number', 'animal'])
>>> df3
letter number animal
0 c 3 cat
1 d 4 dog
>>> pd.concat([df1, df3], sort=False)
letter number animal
0 a 1 NaN
1 b 2 NaN
0 c 3 cat
1 d 4 dog
Combine ``DataFrame`` objects with overlapping columns
and return only those that are shared by passing ``inner`` to
the ``join`` keyword argument.
>>> pd.concat([df1, df3], join="inner")
letter number
0 a 1
1 b 2
0 c 3
1 d 4
Combine ``DataFrame`` objects horizontally along the x axis by
passing in ``axis=1``.
>>> df4 = pd.DataFrame([['bird', 'polly'], ['monkey', 'george']],
... columns=['animal', 'name'])
>>> pd.concat([df1, df4], axis=1)
letter number animal name
0 a 1 bird polly
1 b 2 monkey george
Prevent the result from including duplicate index values with the
``verify_integrity`` option.
>>> df5 = pd.DataFrame([1], index=['a'])
>>> df5
0
a 1
>>> df6 = pd.DataFrame([2], index=['a'])
>>> df6
0
a 2
>>> pd.concat([df5, df6], verify_integrity=True)
Traceback (most recent call last):
...
ValueError: Indexes have overlapping values: ['a']
"""
op = _Concatenator(objs, axis=axis, join_axes=join_axes,
ignore_index=ignore_index, join=join,
keys=keys, levels=levels, names=names,
verify_integrity=verify_integrity,
copy=copy, sort=sort)
return op.get_result()
class _Concatenator(object):
"""
Orchestrates a concatenation operation for BlockManagers
"""
def __init__(self, objs, axis=0, join='outer', join_axes=None,
keys=None, levels=None, names=None,
ignore_index=False, verify_integrity=False, copy=True,
sort=False):
if isinstance(objs, (NDFrame, compat.string_types)):
raise TypeError('first argument must be an iterable of pandas '
'objects, you passed an object of type '
'"{name}"'.format(name=type(objs).__name__))
if join == 'outer':
self.intersect = False
elif join == 'inner':
self.intersect = True
else: # pragma: no cover
raise ValueError('Only can inner (intersect) or outer (union) '
'join the other axis')
if isinstance(objs, dict):
if keys is None:
keys = sorted(objs)
objs = [objs[k] for k in keys]
else:
objs = list(objs)
if len(objs) == 0:
raise ValueError('No objects to concatenate')
if keys is None:
objs = list(com._not_none(*objs))
else:
# #1649
clean_keys = []
clean_objs = []
for k, v in zip(keys, objs):
if v is None:
continue
clean_keys.append(k)
clean_objs.append(v)
objs = clean_objs
name = getattr(keys, 'name', None)
keys = Index(clean_keys, name=name)
if len(objs) == 0:
raise ValueError('All objects passed were None')
# consolidate data & figure out what our result ndim is going to be
ndims = set()
for obj in objs:
if not isinstance(obj, NDFrame):
msg = ('cannot concatenate object of type "{0}";'
' only pd.Series, pd.DataFrame, and pd.Panel'
' (deprecated) objs are valid'.format(type(obj)))
raise TypeError(msg)
# consolidate
obj._consolidate(inplace=True)
ndims.add(obj.ndim)
# get the sample
# want the highest ndim that we have, and must be non-empty
# unless all objs are empty
sample = None
if len(ndims) > 1:
max_ndim = max(ndims)
for obj in objs:
if obj.ndim == max_ndim and np.sum(obj.shape):
sample = obj
break
else:
# filter out the empties if we have not multi-index possibilities
# note to keep empty Series as it affect to result columns / name
non_empties = [obj for obj in objs
if sum(obj.shape) > 0 or isinstance(obj, Series)]
if (len(non_empties) and (keys is None and names is None and
levels is None and
join_axes is None and
not self.intersect)):
objs = non_empties
sample = objs[0]
if sample is None:
sample = objs[0]
self.objs = objs
# Standardize axis parameter to int
if isinstance(sample, Series):
axis = DataFrame._get_axis_number(axis)
else:
axis = sample._get_axis_number(axis)
# Need to flip BlockManager axis in the DataFrame special case
self._is_frame = isinstance(sample, DataFrame)
if self._is_frame:
axis = 1 if axis == 0 else 0
self._is_series = isinstance(sample, Series)
if not 0 <= axis <= sample.ndim:
raise AssertionError("axis must be between 0 and {ndim}, input was"
" {axis}".format(ndim=sample.ndim, axis=axis))
# if we have mixed ndims, then convert to highest ndim
# creating column numbers as needed
if len(ndims) > 1:
current_column = 0
max_ndim = sample.ndim
self.objs, objs = [], self.objs
for obj in objs:
ndim = obj.ndim
if ndim == max_ndim:
pass
elif ndim != max_ndim - 1:
raise ValueError("cannot concatenate unaligned mixed "
"dimensional NDFrame objects")
else:
name = getattr(obj, 'name', None)
if ignore_index or name is None:
name = current_column
current_column += 1
# doing a row-wise concatenation so need everything
# to line up
if self._is_frame and axis == 1:
name = 0
obj = sample._constructor({name: obj})
self.objs.append(obj)
# note: this is the BlockManager axis (since DataFrame is transposed)
self.axis = axis
self.join_axes = join_axes
self.keys = keys
self.names = names or getattr(keys, 'names', None)
self.levels = levels
self.sort = sort
self.ignore_index = ignore_index
self.verify_integrity = verify_integrity
self.copy = copy
self.new_axes = self._get_new_axes()
def get_result(self):
# series only
if self._is_series:
# stack blocks
if self.axis == 0:
name = com.consensus_name_attr(self.objs)
mgr = self.objs[0]._data.concat([x._data for x in self.objs],
self.new_axes)
cons = _concat._get_series_result_type(mgr, self.objs)
return cons(mgr, name=name).__finalize__(self, method='concat')
# combine as columns in a frame
else:
data = dict(zip(range(len(self.objs)), self.objs))
cons = _concat._get_series_result_type(data)
index, columns = self.new_axes
df = cons(data, index=index)
df.columns = columns
return df.__finalize__(self, method='concat')
# combine block managers
else:
mgrs_indexers = []
for obj in self.objs:
mgr = obj._data
indexers = {}
for ax, new_labels in enumerate(self.new_axes):
if ax == self.axis:
# Suppress reindexing on concat axis
continue
obj_labels = mgr.axes[ax]
if not new_labels.equals(obj_labels):
indexers[ax] = obj_labels.reindex(new_labels)[1]
mgrs_indexers.append((obj._data, indexers))
new_data = concatenate_block_managers(
mgrs_indexers, self.new_axes, concat_axis=self.axis,
copy=self.copy)
if not self.copy:
new_data._consolidate_inplace()
cons = _concat._get_frame_result_type(new_data, self.objs)
return (cons._from_axes(new_data, self.new_axes)
.__finalize__(self, method='concat'))
def _get_result_dim(self):
if self._is_series and self.axis == 1:
return 2
else:
return self.objs[0].ndim
def _get_new_axes(self):
ndim = self._get_result_dim()
new_axes = [None] * ndim
if self.join_axes is None:
for i in range(ndim):
if i == self.axis:
continue
new_axes[i] = self._get_comb_axis(i)
else:
if len(self.join_axes) != ndim - 1:
raise AssertionError("length of join_axes must be equal "
"to {length}".format(length=ndim - 1))
# ufff...
indices = compat.lrange(ndim)
indices.remove(self.axis)
for i, ax in zip(indices, self.join_axes):
new_axes[i] = ax
new_axes[self.axis] = self._get_concat_axis()
return new_axes
def _get_comb_axis(self, i):
data_axis = self.objs[0]._get_block_manager_axis(i)
try:
return _get_objs_combined_axis(self.objs, axis=data_axis,
intersect=self.intersect,
sort=self.sort)
except IndexError:
types = [type(x).__name__ for x in self.objs]
raise TypeError("Cannot concatenate list of {types}"
.format(types=types))
def _get_concat_axis(self):
"""
Return index to be used along concatenation axis.
"""
if self._is_series:
if self.axis == 0:
indexes = [x.index for x in self.objs]
elif self.ignore_index:
idx = ibase.default_index(len(self.objs))
return idx
elif self.keys is None:
names = [None] * len(self.objs)
num = 0
has_names = False
for i, x in enumerate(self.objs):
if not isinstance(x, Series):
raise TypeError("Cannot concatenate type 'Series' "
"with object of type {type!r}"
.format(type=type(x).__name__))
if x.name is not None:
names[i] = x.name
has_names = True
else:
names[i] = num
num += 1
if has_names:
return Index(names)
else:
return ibase.default_index(len(self.objs))
else:
return ensure_index(self.keys).set_names(self.names)
else:
indexes = [x._data.axes[self.axis] for x in self.objs]
if self.ignore_index:
idx = ibase.default_index(sum(len(i) for i in indexes))
return idx
if self.keys is None:
concat_axis = _concat_indexes(indexes)
else:
concat_axis = _make_concat_multiindex(indexes, self.keys,
self.levels, self.names)
self._maybe_check_integrity(concat_axis)
return concat_axis
def _maybe_check_integrity(self, concat_index):
if self.verify_integrity:
if not concat_index.is_unique:
overlap = concat_index[concat_index.duplicated()].unique()
raise ValueError('Indexes have overlapping values: '
'{overlap!s}'.format(overlap=overlap))
def _concat_indexes(indexes):
return indexes[0].append(indexes[1:])
def _make_concat_multiindex(indexes, keys, levels=None, names=None):
if ((levels is None and isinstance(keys[0], tuple)) or
(levels is not None and len(levels) > 1)):
zipped = compat.lzip(*keys)
if names is None:
names = [None] * len(zipped)
if levels is None:
_, levels = _factorize_from_iterables(zipped)
else:
levels = [ensure_index(x) for x in levels]
else:
zipped = [keys]
if names is None:
names = [None]
if levels is None:
levels = [ensure_index(keys)]
else:
levels = [ensure_index(x) for x in levels]
if not _all_indexes_same(indexes):
codes_list = []
# things are potentially different sizes, so compute the exact codes
# for each level and pass those to MultiIndex.from_arrays
for hlevel, level in zip(zipped, levels):
to_concat = []
for key, index in zip(hlevel, indexes):
try:
i = level.get_loc(key)
except KeyError:
raise ValueError('Key {key!s} not in level {level!s}'
.format(key=key, level=level))
to_concat.append(np.repeat(i, len(index)))
codes_list.append(np.concatenate(to_concat))
concat_index = _concat_indexes(indexes)
# these go at the end
if isinstance(concat_index, MultiIndex):
levels.extend(concat_index.levels)
codes_list.extend(concat_index.codes)
else:
codes, categories = _factorize_from_iterable(concat_index)
levels.append(categories)
codes_list.append(codes)
if len(names) == len(levels):
names = list(names)
else:
# make sure that all of the passed indices have the same nlevels
if not len({idx.nlevels for idx in indexes}) == 1:
raise AssertionError("Cannot concat indices that do"
" not have the same number of levels")
# also copies
names = names + _get_consensus_names(indexes)
return MultiIndex(levels=levels, codes=codes_list, names=names,
verify_integrity=False)
new_index = indexes[0]
n = len(new_index)
kpieces = len(indexes)
# also copies
new_names = list(names)
new_levels = list(levels)
# construct codes
new_codes = []
# do something a bit more speedy
for hlevel, level in zip(zipped, levels):
hlevel = ensure_index(hlevel)
mapped = level.get_indexer(hlevel)
mask = mapped == -1
if mask.any():
raise ValueError('Values not found in passed level: {hlevel!s}'
.format(hlevel=hlevel[mask]))
new_codes.append(np.repeat(mapped, n))
if isinstance(new_index, MultiIndex):
new_levels.extend(new_index.levels)
new_codes.extend([np.tile(lab, kpieces) for lab in new_index.codes])
else:
new_levels.append(new_index)
new_codes.append(np.tile(np.arange(n), kpieces))
if len(new_names) < len(new_levels):
new_names.extend(new_index.names)
return MultiIndex(levels=new_levels, codes=new_codes, names=new_names,
verify_integrity=False)
