# pylint: disable=E1101,E1103
# pylint: disable=W0703,W0622,W0613,W0201
from pandas.compat import range, text_type, zip
from pandas import compat
from functools import partial
import itertools

import numpy as np

from pandas.core.dtypes.common import (
    _ensure_platform_int,
    is_list_like, is_bool_dtype,
    needs_i8_conversion, is_sparse, is_object_dtype)
from pandas.core.dtypes.cast import maybe_promote
from pandas.core.dtypes.missing import notna

from pandas.core.series import Series
from pandas.core.frame import DataFrame

from pandas.core.sparse.api import SparseDataFrame, SparseSeries
from pandas.core.sparse.array import SparseArray
from pandas._libs.sparse import IntIndex

from pandas.core.arrays import Categorical
from pandas.core.arrays.categorical import _factorize_from_iterable
from pandas.core.sorting import (get_group_index, get_compressed_ids,
                                 compress_group_index, decons_obs_group_ids)

import pandas.core.algorithms as algos
from pandas._libs import algos as _algos, reshape as _reshape

from pandas.core.index import Index, MultiIndex


class _Unstacker(object):
    """
    Helper class to unstack data / pivot with multi-level index

    Parameters
    ----------
    values : ndarray
        Values of DataFrame to "Unstack"
    index : object
        Pandas ``Index``
    level : int or str, default last level
        Level to "unstack". Accepts a name for the level.
    value_columns : Index, optional
        Pandas ``Index`` or ``MultiIndex`` object if unstacking a DataFrame
    fill_value : scalar, optional
        Default value to fill in missing values if subgroups do not have the
        same set of labels. By default, missing values will be replaced with
        the default fill value for that data type, NaN for float, NaT for
        datetimelike, etc. For integer types, by default data will converted to
        float and missing values will be set to NaN.
    constructor : object
        Pandas ``DataFrame`` or subclass used to create unstacked
        response.  If None, DataFrame or SparseDataFrame will be used.

    Examples
    --------
    >>> import pandas as pd
    >>> index = pd.MultiIndex.from_tuples([('one', 'a'), ('one', 'b'),
    ...                                    ('two', 'a'), ('two', 'b')])
    >>> s = pd.Series(np.arange(1, 5, dtype=np.int64), index=index)
    >>> s
    one  a    1
         b    2
    two  a    3
         b    4
    dtype: int64

    >>> s.unstack(level=-1)
         a  b
    one  1  2
    two  3  4

    >>> s.unstack(level=0)
       one  two
    a    1    3
    b    2    4

    Returns
    -------
    unstacked : DataFrame
    """

    def __init__(self, values, index, level=-1, value_columns=None,
                 fill_value=None, constructor=None):

        self.is_categorical = None
        self.is_sparse = is_sparse(values)
        if values.ndim == 1:
            if isinstance(values, Categorical):
                self.is_categorical = values
                values = np.array(values)
            elif self.is_sparse:
                # XXX: Makes SparseArray *dense*, but it's supposedly
                # a single column at a time, so it's "doable"
                values = values.values
            values = values[:, np.newaxis]
        self.values = values
        self.value_columns = value_columns
        self.fill_value = fill_value

        if constructor is None:
            if self.is_sparse:
                self.constructor = SparseDataFrame
            else:
                self.constructor = DataFrame
        else:
            self.constructor = constructor

        if value_columns is None and values.shape[1] != 1:  # pragma: no cover
            raise ValueError('must pass column labels for multi-column data')

        self.index = index.remove_unused_levels()

        if isinstance(self.index, MultiIndex):
            if index._reference_duplicate_name(level):
                msg = ("Ambiguous reference to {level}. The index "
                       "names are not unique.".format(level=level))
                raise ValueError(msg)

        self.level = self.index._get_level_number(level)

        # when index includes `nan`, need to lift levels/strides by 1
        self.lift = 1 if -1 in self.index.labels[self.level] else 0

        self.new_index_levels = list(self.index.levels)
        self.new_index_names = list(self.index.names)

        self.removed_name = self.new_index_names.pop(self.level)
        self.removed_level = self.new_index_levels.pop(self.level)
        self.removed_level_full = index.levels[self.level]

        self._make_sorted_values_labels()
        self._make_selectors()

    def _make_sorted_values_labels(self):
        v = self.level

        labs = list(self.index.labels)
        levs = list(self.index.levels)
        to_sort = labs[:v] + labs[v + 1:] + [labs[v]]
        sizes = [len(x) for x in levs[:v] + levs[v + 1:] + [levs[v]]]

        comp_index, obs_ids = get_compressed_ids(to_sort, sizes)
        ngroups = len(obs_ids)

        indexer = _algos.groupsort_indexer(comp_index, ngroups)[0]
        indexer = _ensure_platform_int(indexer)

        self.sorted_values = algos.take_nd(self.values, indexer, axis=0)
        self.sorted_labels = [l.take(indexer) for l in to_sort]

    def _make_selectors(self):
        new_levels = self.new_index_levels

        # make the mask
        remaining_labels = self.sorted_labels[:-1]
        level_sizes = [len(x) for x in new_levels]

        comp_index, obs_ids = get_compressed_ids(remaining_labels, level_sizes)
        ngroups = len(obs_ids)

        comp_index = _ensure_platform_int(comp_index)
        stride = self.index.levshape[self.level] + self.lift
        self.full_shape = ngroups, stride

        selector = self.sorted_labels[-1] + stride * comp_index + self.lift
        mask = np.zeros(np.prod(self.full_shape), dtype=bool)
        mask.put(selector, True)

        if mask.sum() < len(self.index):
            raise ValueError('Index contains duplicate entries, '
                             'cannot reshape')

        self.group_index = comp_index
        self.mask = mask
        self.unique_groups = obs_ids
        self.compressor = comp_index.searchsorted(np.arange(ngroups))

    def get_result(self):
        values, _ = self.get_new_values()
        columns = self.get_new_columns()
        index = self.get_new_index()

        # may need to coerce categoricals here
        if self.is_categorical is not None:
            categories = self.is_categorical.categories
            ordered = self.is_categorical.ordered
            values = [Categorical(values[:, i], categories=categories,
                                  ordered=ordered)
                      for i in range(values.shape[-1])]

        return self.constructor(values, index=index, columns=columns)

    def get_new_values(self):
        values = self.values

        # place the values
        length, width = self.full_shape
        stride = values.shape[1]
        result_width = width * stride
        result_shape = (length, result_width)
        mask = self.mask
        mask_all = mask.all()

        # we can simply reshape if we don't have a mask
        if mask_all and len(values):
            new_values = (self.sorted_values
                              .reshape(length, width, stride)
                              .swapaxes(1, 2)
                              .reshape(result_shape)
                          )
            new_mask = np.ones(result_shape, dtype=bool)
            return new_values, new_mask

        # if our mask is all True, then we can use our existing dtype
        if mask_all:
            dtype = values.dtype
            new_values = np.empty(result_shape, dtype=dtype)
        else:
            dtype, fill_value = maybe_promote(values.dtype, self.fill_value)
            new_values = np.empty(result_shape, dtype=dtype)
            new_values.fill(fill_value)

        new_mask = np.zeros(result_shape, dtype=bool)

        name = np.dtype(dtype).name
        sorted_values = self.sorted_values

        # we need to convert to a basic dtype
        # and possibly coerce an input to our output dtype
        # e.g. ints -> floats
        if needs_i8_conversion(values):
            sorted_values = sorted_values.view('i8')
            new_values = new_values.view('i8')
            name = 'int64'
        elif is_bool_dtype(values):
            sorted_values = sorted_values.astype('object')
            new_values = new_values.astype('object')
            name = 'object'
        else:
            sorted_values = sorted_values.astype(name, copy=False)

        # fill in our values & mask
        f = getattr(_reshape, "unstack_{name}".format(name=name))
        f(sorted_values,
          mask.view('u1'),
          stride,
          length,
          width,
          new_values,
          new_mask.view('u1'))

        # reconstruct dtype if needed
        if needs_i8_conversion(values):
            new_values = new_values.view(values.dtype)

        return new_values, new_mask

    def get_new_columns(self):
        if self.value_columns is None:
            if self.lift == 0:
                return self.removed_level

            lev = self.removed_level
            return lev.insert(0, lev._na_value)

        stride = len(self.removed_level) + self.lift
        width = len(self.value_columns)
        propagator = np.repeat(np.arange(width), stride)
        if isinstance(self.value_columns, MultiIndex):
            new_levels = self.value_columns.levels + (self.removed_level_full,)
            new_names = self.value_columns.names + (self.removed_name,)

            new_labels = [lab.take(propagator)
                          for lab in self.value_columns.labels]
        else:
            new_levels = [self.value_columns, self.removed_level_full]
            new_names = [self.value_columns.name, self.removed_name]
            new_labels = [propagator]

        # The two indices differ only if the unstacked level had unused items:
        if len(self.removed_level_full) != len(self.removed_level):
            # In this case, we remap the new labels to the original level:
            repeater = self.removed_level_full.get_indexer(self.removed_level)
            if self.lift:
                repeater = np.insert(repeater, 0, -1)
        else:
            # Otherwise, we just use each level item exactly once:
            repeater = np.arange(stride) - self.lift

        # The entire level is then just a repetition of the single chunk:
        new_labels.append(np.tile(repeater, width))
        return MultiIndex(levels=new_levels, labels=new_labels,
                          names=new_names, verify_integrity=False)

    def get_new_index(self):
        result_labels = [lab.take(self.compressor)
                         for lab in self.sorted_labels[:-1]]

        # construct the new index
        if len(self.new_index_levels) == 1:
            lev, lab = self.new_index_levels[0], result_labels[0]
            if (lab == -1).any():
                lev = lev.insert(len(lev), lev._na_value)
            return lev.take(lab)

        return MultiIndex(levels=self.new_index_levels, labels=result_labels,
                          names=self.new_index_names, verify_integrity=False)


def _unstack_multiple(data, clocs, fill_value=None):
    if len(clocs) == 0:
        return data

    # NOTE: This doesn't deal with hierarchical columns yet

    index = data.index

    clocs = [index._get_level_number(i) for i in clocs]

    rlocs = [i for i in range(index.nlevels) if i not in clocs]

    clevels = [index.levels[i] for i in clocs]
    clabels = [index.labels[i] for i in clocs]
    cnames = [index.names[i] for i in clocs]
    rlevels = [index.levels[i] for i in rlocs]
    rlabels = [index.labels[i] for i in rlocs]
    rnames = [index.names[i] for i in rlocs]

    shape = [len(x) for x in clevels]
    group_index = get_group_index(clabels, shape, sort=False, xnull=False)

    comp_ids, obs_ids = compress_group_index(group_index, sort=False)
    recons_labels = decons_obs_group_ids(comp_ids, obs_ids, shape, clabels,
                                         xnull=False)

    if rlocs == []:
        # Everything is in clocs, so the dummy df has a regular index
        dummy_index = Index(obs_ids, name='__placeholder__')
    else:
        dummy_index = MultiIndex(levels=rlevels + [obs_ids],
                                 labels=rlabels + [comp_ids],
                                 names=rnames + ['__placeholder__'],
                                 verify_integrity=False)

    if isinstance(data, Series):
        dummy = data.copy()
        dummy.index = dummy_index
        unstacked = dummy.unstack('__placeholder__', fill_value=fill_value)
        new_levels = clevels
        new_names = cnames
        new_labels = recons_labels
    else:
        if isinstance(data.columns, MultiIndex):
            result = data
            for i in range(len(clocs)):
                val = clocs[i]
                result = result.unstack(val)
                clocs = [v if i > v else v - 1 for v in clocs]

            return result

        dummy = data.copy()
        dummy.index = dummy_index

        unstacked = dummy.unstack('__placeholder__', fill_value=fill_value)
        if isinstance(unstacked, Series):
            unstcols = unstacked.index
        else:
            unstcols = unstacked.columns
        new_levels = [unstcols.levels[0]] + clevels
        new_names = [data.columns.name] + cnames

        new_labels = [unstcols.labels[0]]
        for rec in recons_labels:
            new_labels.append(rec.take(unstcols.labels[-1]))

    new_columns = MultiIndex(levels=new_levels, labels=new_labels,
                             names=new_names, verify_integrity=False)

    if isinstance(unstacked, Series):
        unstacked.index = new_columns
    else:
        unstacked.columns = new_columns

    return unstacked


def pivot(self, index=None, columns=None, values=None):
    """
    See DataFrame.pivot
    """
    if values is None:
        cols = [columns] if index is None else [index, columns]
        append = index is None
        indexed = self.set_index(cols, append=append)
    else:
        if index is None:
            index = self.index
        else:
            index = self[index]
        index = MultiIndex.from_arrays([index, self[columns]])

        if is_list_like(values) and not isinstance(values, tuple):
            # Exclude tuple because it is seen as a single column name
            indexed = self._constructor(self[values].values, index=index,
                                        columns=values)
        else:
            indexed = self._constructor_sliced(self[values].values,
                                               index=index)
    return indexed.unstack(columns)


def pivot_simple(index, columns, values):
    """
    Produce 'pivot' table based on 3 columns of this DataFrame.
    Uses unique values from index / columns and fills with values.

    Parameters
    ----------
    index : ndarray
        Labels to use to make new frame's index
    columns : ndarray
        Labels to use to make new frame's columns
    values : ndarray
        Values to use for populating new frame's values

    Notes
    -----
    Obviously, all 3 of the input arguments must have the same length

    Returns
    -------
    DataFrame

    See also
    --------
    DataFrame.pivot_table : generalization of pivot that can handle
        duplicate values for one index/column pair
    """
    if (len(index) != len(columns)) or (len(columns) != len(values)):
        raise AssertionError('Length of index, columns, and values must be the'
                             ' same')

    if len(index) == 0:
        return DataFrame(index=[])

    hindex = MultiIndex.from_arrays([index, columns])
    series = Series(values.ravel(), index=hindex)
    series = series.sort_index(level=0)
    return series.unstack()


def _slow_pivot(index, columns, values):
    """
    Produce 'pivot' table based on 3 columns of this DataFrame.
    Uses unique values from index / columns and fills with values.

    Parameters
    ----------
    index : string or object
        Column name to use to make new frame's index
    columns : string or object
        Column name to use to make new frame's columns
    values : string or object
        Column name to use for populating new frame's values

    Could benefit from some Cython here.
    """
    tree = {}
    for i, (idx, col) in enumerate(zip(index, columns)):
        if col not in tree:
            tree[col] = {}
        branch = tree[col]
        branch[idx] = values[i]

    return DataFrame(tree)


def unstack(obj, level, fill_value=None):
    if isinstance(level, (tuple, list)):
        if len(level) != 1:
            # _unstack_multiple only handles MultiIndexes,
            # and isn't needed for a single level
            return _unstack_multiple(obj, level, fill_value=fill_value)
        else:
            level = level[0]

    if isinstance(obj, DataFrame):
        if isinstance(obj.index, MultiIndex):
            return _unstack_frame(obj, level, fill_value=fill_value)
        else:
            return obj.T.stack(dropna=False)
    else:
        unstacker = _Unstacker(obj.values, obj.index, level=level,
                               fill_value=fill_value,
                               constructor=obj._constructor_expanddim)
        return unstacker.get_result()


def _unstack_frame(obj, level, fill_value=None):
    if obj._is_mixed_type:
        unstacker = partial(_Unstacker, index=obj.index,
                            level=level, fill_value=fill_value)
        blocks = obj._data.unstack(unstacker)
        return obj._constructor(blocks)
    else:
        unstacker = _Unstacker(obj.values, obj.index, level=level,
                               value_columns=obj.columns,
                               fill_value=fill_value,
                               constructor=obj._constructor)
        return unstacker.get_result()


def stack(frame, level=-1, dropna=True):
    """
    Convert DataFrame to Series with multi-level Index. Columns become the
    second level of the resulting hierarchical index

    Returns
    -------
    stacked : Series
    """

    def factorize(index):
        if index.is_unique:
            return index, np.arange(len(index))
        codes, categories = _factorize_from_iterable(index)
        return categories, codes

    N, K = frame.shape

    if isinstance(frame.columns, MultiIndex):
        if frame.columns._reference_duplicate_name(level):
            msg = ("Ambiguous reference to {level}. The column "
                   "names are not unique.".format(level=level))
            raise ValueError(msg)

    # Will also convert negative level numbers and check if out of bounds.
    level_num = frame.columns._get_level_number(level)

    if isinstance(frame.columns, MultiIndex):
        return _stack_multi_columns(frame, level_num=level_num, dropna=dropna)
    elif isinstance(frame.index, MultiIndex):
        new_levels = list(frame.index.levels)
        new_labels = [lab.repeat(K) for lab in frame.index.labels]

        clev, clab = factorize(frame.columns)
        new_levels.append(clev)
        new_labels.append(np.tile(clab, N).ravel())

        new_names = list(frame.index.names)
        new_names.append(frame.columns.name)
        new_index = MultiIndex(levels=new_levels, labels=new_labels,
                               names=new_names, verify_integrity=False)
    else:
        levels, (ilab, clab) = zip(*map(factorize, (frame.index,
                                                    frame.columns)))
        labels = ilab.repeat(K), np.tile(clab, N).ravel()
        new_index = MultiIndex(levels=levels, labels=labels,
                               names=[frame.index.name, frame.columns.name],
                               verify_integrity=False)

    new_values = frame.values.ravel()
    if dropna:
        mask = notna(new_values)
        new_values = new_values[mask]
        new_index = new_index[mask]

    return frame._constructor_sliced(new_values, index=new_index)


def stack_multiple(frame, level, dropna=True):
    # If all passed levels match up to column names, no
    # ambiguity about what to do
    if all(lev in frame.columns.names for lev in level):
        result = frame
        for lev in level:
            result = stack(result, lev, dropna=dropna)

    # Otherwise, level numbers may change as each successive level is stacked
    elif all(isinstance(lev, int) for lev in level):
        # As each stack is done, the level numbers decrease, so we need
        #  to account for that when level is a sequence of ints
        result = frame
        # _get_level_number() checks level numbers are in range and converts
        # negative numbers to positive
        level = [frame.columns._get_level_number(lev) for lev in level]

        # Can't iterate directly through level as we might need to change
        # values as we go
        for index in range(len(level)):
            lev = level[index]
            result = stack(result, lev, dropna=dropna)
            # Decrement all level numbers greater than current, as these
            # have now shifted down by one
            updated_level = []
            for other in level:
                if other > lev:
                    updated_level.append(other - 1)
                else:
                    updated_level.append(other)
            level = updated_level

    else:
        raise ValueError("level should contain all level names or all level "
                         "numbers, not a mixture of the two.")

    return result


def _stack_multi_columns(frame, level_num=-1, dropna=True):
    def _convert_level_number(level_num, columns):
        """
        Logic for converting the level number to something we can safely pass
        to swaplevel:

        We generally want to convert the level number into a level name, except
        when columns do not have names, in which case we must leave as a level
        number
        """
        if level_num in columns.names:
            return columns.names[level_num]
        else:
            if columns.names[level_num] is None:
                return level_num
            else:
                return columns.names[level_num]

    this = frame.copy()

    # this makes life much simpler
    if level_num != frame.columns.nlevels - 1:
        # roll levels to put selected level at end
        roll_columns = this.columns
        for i in range(level_num, frame.columns.nlevels - 1):
            # Need to check if the ints conflict with level names
            lev1 = _convert_level_number(i, roll_columns)
            lev2 = _convert_level_number(i + 1, roll_columns)
            roll_columns = roll_columns.swaplevel(lev1, lev2)
        this.columns = roll_columns

    if not this.columns.is_lexsorted():
        # Workaround the edge case where 0 is one of the column names,
        # which interferes with trying to sort based on the first
        # level
        level_to_sort = _convert_level_number(0, this.columns)
        this = this.sort_index(level=level_to_sort, axis=1)

    # tuple list excluding level for grouping columns
    if len(frame.columns.levels) > 2:
        tuples = list(zip(*[lev.take(lab)
                            for lev, lab in zip(this.columns.levels[:-1],
                                                this.columns.labels[:-1])]))
        unique_groups = [key for key, _ in itertools.groupby(tuples)]
        new_names = this.columns.names[:-1]
        new_columns = MultiIndex.from_tuples(unique_groups, names=new_names)
    else:
        new_columns = unique_groups = this.columns.levels[0]

    # time to ravel the values
    new_data = {}
    level_vals = this.columns.levels[-1]
    level_labels = sorted(set(this.columns.labels[-1]))
    level_vals_used = level_vals[level_labels]
    levsize = len(level_labels)
    drop_cols = []
    for key in unique_groups:
        try:
            loc = this.columns.get_loc(key)
        except KeyError:
            drop_cols.append(key)
            continue

        # can make more efficient?
        # we almost always return a slice
        # but if unsorted can get a boolean
        # indexer
        if not isinstance(loc, slice):
            slice_len = len(loc)
        else:
            slice_len = loc.stop - loc.start

        if slice_len != levsize:
            chunk = this.loc[:, this.columns[loc]]
            chunk.columns = level_vals.take(chunk.columns.labels[-1])
            value_slice = chunk.reindex(columns=level_vals_used).values
        else:
            if frame._is_mixed_type:
                value_slice = this.loc[:, this.columns[loc]].values
            else:
                value_slice = this.values[:, loc]

        new_data[key] = value_slice.ravel()

    if len(drop_cols) > 0:
        new_columns = new_columns.difference(drop_cols)

    N = len(this)

    if isinstance(this.index, MultiIndex):
        new_levels = list(this.index.levels)
        new_names = list(this.index.names)
        new_labels = [lab.repeat(levsize) for lab in this.index.labels]
    else:
        new_levels = [this.index]
        new_labels = [np.arange(N).repeat(levsize)]
        new_names = [this.index.name]  # something better?

    new_levels.append(level_vals)
    new_labels.append(np.tile(level_labels, N))
    new_names.append(frame.columns.names[level_num])

    new_index = MultiIndex(levels=new_levels, labels=new_labels,
                           names=new_names, verify_integrity=False)

    result = frame._constructor(new_data, index=new_index, columns=new_columns)

    # more efficient way to go about this? can do the whole masking biz but
    # will only save a small amount of time...
    if dropna:
        result = result.dropna(axis=0, how='all')

    return result


def get_dummies(data, prefix=None, prefix_sep='_', dummy_na=False,
                columns=None, sparse=False, drop_first=False, dtype=None):
    """
    Convert categorical variable into dummy/indicator variables

    Parameters
    ----------
    data : array-like, Series, or DataFrame
    prefix : string, list of strings, or dict of strings, default None
        String to append DataFrame column names.
        Pass a list with length equal to the number of columns
        when calling get_dummies on a DataFrame. Alternatively, `prefix`
        can be a dictionary mapping column names to prefixes.
    prefix_sep : string, default '_'
        If appending prefix, separator/delimiter to use. Or pass a
        list or dictionary as with `prefix.`
    dummy_na : bool, default False
        Add a column to indicate NaNs, if False NaNs are ignored.
    columns : list-like, default None
        Column names in the DataFrame to be encoded.
        If `columns` is None then all the columns with
        `object` or `category` dtype will be converted.
    sparse : bool, default False
        Whether the dummy columns should be sparse or not.  Returns
        SparseDataFrame if `data` is a Series or if all columns are included.
        Otherwise returns a DataFrame with some SparseBlocks.
    drop_first : bool, default False
        Whether to get k-1 dummies out of k categorical levels by removing the
        first level.

        .. versionadded:: 0.18.0

    dtype : dtype, default np.uint8
        Data type for new columns. Only a single dtype is allowed.

        .. versionadded:: 0.23.0

    Returns
    -------
    dummies : DataFrame or SparseDataFrame

    Examples
    --------
    >>> import pandas as pd
    >>> s = pd.Series(list('abca'))

    >>> pd.get_dummies(s)
       a  b  c
    0  1  0  0
    1  0  1  0
    2  0  0  1
    3  1  0  0

    >>> s1 = ['a', 'b', np.nan]

    >>> pd.get_dummies(s1)
       a  b
    0  1  0
    1  0  1
    2  0  0

    >>> pd.get_dummies(s1, dummy_na=True)
       a  b  NaN
    0  1  0    0
    1  0  1    0
    2  0  0    1

    >>> df = pd.DataFrame({'A': ['a', 'b', 'a'], 'B': ['b', 'a', 'c'],
    ...                    'C': [1, 2, 3]})

    >>> pd.get_dummies(df, prefix=['col1', 'col2'])
       C  col1_a  col1_b  col2_a  col2_b  col2_c
    0  1       1       0       0       1       0
    1  2       0       1       1       0       0
    2  3       1       0       0       0       1

    >>> pd.get_dummies(pd.Series(list('abcaa')))
       a  b  c
    0  1  0  0
    1  0  1  0
    2  0  0  1
    3  1  0  0
    4  1  0  0

    >>> pd.get_dummies(pd.Series(list('abcaa')), drop_first=True)
       b  c
    0  0  0
    1  1  0
    2  0  1
    3  0  0
    4  0  0

    >>> pd.get_dummies(pd.Series(list('abc')), dtype=float)
         a    b    c
    0  1.0  0.0  0.0
    1  0.0  1.0  0.0
    2  0.0  0.0  1.0

    See Also
    --------
    Series.str.get_dummies
    """
    from pandas.core.reshape.concat import concat
    from itertools import cycle

    dtypes_to_encode = ['object', 'category']

    if isinstance(data, DataFrame):
        # determine columns being encoded
        if columns is None:
            data_to_encode = data.select_dtypes(
                include=dtypes_to_encode)
        else:
            data_to_encode = data[columns]

        # validate prefixes and separator to avoid silently dropping cols
        def check_len(item, name):
            len_msg = ("Length of '{name}' ({len_item}) did not match the "
                       "length of the columns being encoded ({len_enc}).")

            if is_list_like(item):
                if not len(item) == data_to_encode.shape[1]:
                    len_msg = \
                        len_msg.format(name=name, len_item=len(item),
                                       len_enc=data_to_encode.shape[1])
                    raise ValueError(len_msg)

        check_len(prefix, 'prefix')
        check_len(prefix_sep, 'prefix_sep')

        if isinstance(prefix, compat.string_types):
            prefix = cycle([prefix])
        if isinstance(prefix, dict):
            prefix = [prefix[col] for col in data_to_encode.columns]

        if prefix is None:
            prefix = data_to_encode.columns

        # validate separators
        if isinstance(prefix_sep, compat.string_types):
            prefix_sep = cycle([prefix_sep])
        elif isinstance(prefix_sep, dict):
            prefix_sep = [prefix_sep[col] for col in data_to_encode.columns]

        if data_to_encode.shape == data.shape:
            # Encoding the entire df, do not prepend any dropped columns
            with_dummies = []
        elif columns is not None:
            # Encoding only cols specified in columns. Get all cols not in
            # columns to prepend to result.
            with_dummies = [data.drop(columns, axis=1)]
        else:
            # Encoding only object and category dtype columns. Get remaining
            # columns to prepend to result.
            with_dummies = [data.select_dtypes(exclude=dtypes_to_encode)]

        for (col, pre, sep) in zip(data_to_encode.iteritems(), prefix,
                                   prefix_sep):
            # col is (column_name, column), use just column data here
            dummy = _get_dummies_1d(col[1], prefix=pre, prefix_sep=sep,
                                    dummy_na=dummy_na, sparse=sparse,
                                    drop_first=drop_first, dtype=dtype)
            with_dummies.append(dummy)
        result = concat(with_dummies, axis=1)
    else:
        result = _get_dummies_1d(data, prefix, prefix_sep, dummy_na,
                                 sparse=sparse,
                                 drop_first=drop_first,
                                 dtype=dtype)
    return result


def _get_dummies_1d(data, prefix, prefix_sep='_', dummy_na=False,
                    sparse=False, drop_first=False, dtype=None):
    # Series avoids inconsistent NaN handling
    codes, levels = _factorize_from_iterable(Series(data))

    if dtype is None:
        dtype = np.uint8
    dtype = np.dtype(dtype)

    if is_object_dtype(dtype):
        raise ValueError("dtype=object is not a valid dtype for get_dummies")

    def get_empty_Frame(data, sparse):
        if isinstance(data, Series):
            index = data.index
        else:
            index = np.arange(len(data))
        if not sparse:
            return DataFrame(index=index)
        else:
            return SparseDataFrame(index=index, default_fill_value=0)

    # if all NaN
    if not dummy_na and len(levels) == 0:
        return get_empty_Frame(data, sparse)

    codes = codes.copy()
    if dummy_na:
        codes[codes == -1] = len(levels)
        levels = np.append(levels, np.nan)

    # if dummy_na, we just fake a nan level. drop_first will drop it again
    if drop_first and len(levels) == 1:
        return get_empty_Frame(data, sparse)

    number_of_cols = len(levels)

    if prefix is not None:
        dummy_strs = [u'{prefix}{sep}{level}' if isinstance(v, text_type)
                      else '{prefix}{sep}{level}' for v in levels]
        dummy_cols = [dummy_str.format(prefix=prefix, sep=prefix_sep, level=v)
                      for dummy_str, v in zip(dummy_strs, levels)]
    else:
        dummy_cols = levels

    if isinstance(data, Series):
        index = data.index
    else:
        index = None

    if sparse:
        sparse_series = {}
        N = len(data)
        sp_indices = [[] for _ in range(len(dummy_cols))]
        for ndx, code in enumerate(codes):
            if code == -1:
                # Blank entries if not dummy_na and code == -1, #GH4446
                continue
            sp_indices[code].append(ndx)

        if drop_first:
            # remove first categorical level to avoid perfect collinearity
            # GH12042
            sp_indices = sp_indices[1:]
            dummy_cols = dummy_cols[1:]
        for col, ixs in zip(dummy_cols, sp_indices):
            sarr = SparseArray(np.ones(len(ixs), dtype=dtype),
                               sparse_index=IntIndex(N, ixs), fill_value=0,
                               dtype=dtype)
            sparse_series[col] = SparseSeries(data=sarr, index=index)

        out = SparseDataFrame(sparse_series, index=index, columns=dummy_cols,
                              default_fill_value=0,
                              dtype=dtype)
        return out

    else:
        dummy_mat = np.eye(number_of_cols, dtype=dtype).take(codes, axis=0)

        if not dummy_na:
            # reset NaN GH4446
            dummy_mat[codes == -1] = 0

        if drop_first:
            # remove first GH12042
            dummy_mat = dummy_mat[:, 1:]
            dummy_cols = dummy_cols[1:]
        return DataFrame(dummy_mat, index=index, columns=dummy_cols)


def make_axis_dummies(frame, axis='minor', transform=None):
    """
    Construct 1-0 dummy variables corresponding to designated axis
    labels

    Parameters
    ----------
    frame : DataFrame
    axis : {'major', 'minor'}, default 'minor'
    transform : function, default None
        Function to apply to axis labels first. For example, to
        get "day of week" dummies in a time series regression
        you might call::

            make_axis_dummies(panel, axis='major',
                              transform=lambda d: d.weekday())
    Returns
    -------
    dummies : DataFrame
        Column names taken from chosen axis
    """
    numbers = {'major': 0, 'minor': 1}
    num = numbers.get(axis, axis)

    items = frame.index.levels[num]
    labels = frame.index.labels[num]
    if transform is not None:
        mapped_items = items.map(transform)
        labels, items = _factorize_from_iterable(mapped_items.take(labels))

    values = np.eye(len(items), dtype=float)
    values = values.take(labels, axis=0)

    return DataFrame(values, columns=items, index=frame.index)