indexing.py

# pylint: disable=W0223

from datetime import datetime
from pandas.core.index import Index, MultiIndex, _ensure_index
from pandas.compat import range, zip
import pandas.compat as compat
import pandas.core.common as com
from pandas.core.common import (_is_bool_indexer, is_integer_dtype,
                                _asarray_tuplesafe, is_list_like, isnull,
                                ABCSeries, ABCDataFrame, ABCPanel)
import pandas.lib as lib

import numpy as np

# the supported indexers
def get_indexers_list():

    return [
        ('ix',   _IXIndexer),
        ('iloc', _iLocIndexer),
        ('loc',  _LocIndexer),
        ('at',   _AtIndexer),
        ('iat',  _iAtIndexer),
    ]

# "null slice"
_NS = slice(None, None)

# the public IndexSlicerMaker
class _IndexSlice(object):
    def __getitem__(self, arg):
        return arg
IndexSlice = _IndexSlice()

class IndexingError(Exception):
    pass


class _NDFrameIndexer(object):
    _valid_types = None
    _exception = KeyError

    def __init__(self, obj, name):
        self.obj = obj
        self.ndim = obj.ndim
        self.name = name
        self.axis = None

    def __call__(self, *args, **kwargs):
        # we need to return a copy of ourselves
        self = self.__class__(self.obj, self.name)

        # set the passed in values
        for k, v in compat.iteritems(kwargs):
            setattr(self,k,v)
        return self

    def __iter__(self):
        raise NotImplementedError('ix is not iterable')

    def __getitem__(self, key):
        if type(key) is tuple:
            try:
                return self.obj.get_value(*key)
            except Exception:
                pass

            return self._getitem_tuple(key)
        else:
            return self._getitem_axis(key, axis=0)

    def _get_label(self, label, axis=0):
        if self.ndim == 1:
            # for perf reasons we want to try _xs first
            # as its basically direct indexing
            # but will fail when the index is not present
            # see GH5667
            try:
                return self.obj._xs(label, axis=axis, copy=False)
            except:
                return self.obj[label]
        elif (isinstance(label, tuple) and
                isinstance(label[axis], slice)):
            raise IndexingError('no slices here, handle elsewhere')

        try:
            return self.obj._xs(label, axis=axis, copy=False)
        except Exception:
            return self.obj._xs(label, axis=axis, copy=True)

    def _get_loc(self, key, axis=0):
        return self.obj._ixs(key, axis=axis)

    def _slice(self, obj, axis=0, raise_on_error=False, typ=None):

        # make out-of-bounds into bounds of the object
        if typ == 'iloc':
            ax = self.obj._get_axis(axis)
            l = len(ax)
            start = obj.start
            stop = obj.stop
            step = obj.step
            if start is not None:
                # degenerate to return nothing
                if start >= l:
                    return self._getitem_axis(tuple(),axis=axis)

                # equiv to a null slice
                elif start <= -l:
                    start = None
            if stop is not None:
                if stop > l:
                    stop = None
                elif stop <= -l:
                    stop = None
            obj = slice(start,stop,step)

        return self.obj._slice(obj, axis=axis, raise_on_error=raise_on_error,
                               typ=typ)

    def __setitem__(self, key, value):

        if self.axis is not None:
            indexer = self._convert_tuple(key, is_setter=True)

        else:

            # kludgetastic
            ax = self.obj._get_axis(0)
            if isinstance(ax, MultiIndex):
                try:
                    indexer = ax.get_loc(key)
                    self._setitem_with_indexer(indexer, value)
                    return
                except Exception:
                    pass

            if isinstance(key, tuple):
                if len(key) > self.ndim:
                    raise IndexingError('only tuples of length <= %d supported' %
                                        self.ndim)
                indexer = self._convert_tuple(key, is_setter=True)
            else:
                indexer = self._convert_to_indexer(key, is_setter=True)

        self._setitem_with_indexer(indexer, value)

    def _has_valid_type(self, k, axis):
        raise NotImplementedError()

    def _has_valid_tuple(self, key):
        """ check the key for valid keys across my indexer """
        for i, k in enumerate(key):
            if i >= self.obj.ndim:
                raise IndexingError('Too many indexers')
            if not self._has_valid_type(k, i):
                raise ValueError("Location based indexing can only have [%s] "
                                 "types" % self._valid_types)

    def _is_nested_tuple_indexer(self, tup):
        if any([ isinstance(ax, MultiIndex) for ax in self.obj.axes ]):
            return any([ _is_nested_tuple(tup,ax) for ax in self.obj.axes ])
        return False

    def _convert_tuple(self, key, is_setter=False):
        keyidx = []
        if self.axis is not None:
            axis = self.obj._get_axis_number(self.axis)
            for i in range(self.ndim):
                if i == axis:
                    keyidx.append(self._convert_to_indexer(key, axis=axis, is_setter=is_setter))
                else:
                    keyidx.append(slice(None))
        else:
            for i, k in enumerate(key):
                idx = self._convert_to_indexer(k, axis=i, is_setter=is_setter)
                keyidx.append(idx)
        return tuple(keyidx)

    def _convert_scalar_indexer(self, key, axis):
        # if we are accessing via lowered dim, use the last dim
        ax = self.obj._get_axis(min(axis, self.ndim - 1))
        # a scalar
        return ax._convert_scalar_indexer(key, typ=self.name)

    def _convert_slice_indexer(self, key, axis):
        # if we are accessing via lowered dim, use the last dim
        ax = self.obj._get_axis(min(axis, self.ndim - 1))
        return ax._convert_slice_indexer(key, typ=self.name)

    def _has_valid_setitem_indexer(self, indexer):
        return True

    def _has_valid_positional_setitem_indexer(self, indexer):
        """ validate that an positional indexer cannot enlarge its target
            will raise if needed, does not modify the indexer externally """
        if isinstance(indexer, dict):
            raise IndexError("{0} cannot enlarge its target object"
                             .format(self.name))
        else:
            if not isinstance(indexer, tuple):
                indexer = self._tuplify(indexer)
            for ax, i in zip(self.obj.axes, indexer):
                if isinstance(i, slice):
                    # should check the stop slice?
                    pass
                elif is_list_like(i):
                    # should check the elements?
                    pass
                elif com.is_integer(i):
                    if i >= len(ax):
                        raise IndexError("{0} cannot enlarge its target object"
                                         .format(self.name))
                elif isinstance(i, dict):
                    raise IndexError("{0} cannot enlarge its target object"
                                     .format(self.name))

        return True

    def _setitem_with_indexer(self, indexer, value):

        self._has_valid_setitem_indexer(indexer)

        # also has the side effect of consolidating in-place
        from pandas import Panel, DataFrame, Series

        # maybe partial set
        take_split_path = self.obj._is_mixed_type
        if isinstance(indexer, tuple):
            nindexer = []
            for i, idx in enumerate(indexer):
                if isinstance(idx, dict):

                    # reindex the axis to the new value
                    # and set inplace
                    key, _ = _convert_missing_indexer(idx)

                    # if this is the items axes, then take the main missing
                    # path first
                    # this correctly sets the dtype and avoids cache issues
                    # essentially this separates out the block that is needed
                    # to possibly be modified
                    if self.ndim > 1 and i == self.obj._info_axis_number:

                        # add the new item, and set the value
                        # must have all defined axes if we have a scalar
                        # or a list-like on the non-info axes if we have a
                        # list-like
                        len_non_info_axes = [
                            len(_ax) for _i, _ax in enumerate(self.obj.axes)
                            if _i != i
                        ]
                        if any([not l for l in len_non_info_axes]):
                            if not is_list_like(value):
                                raise ValueError("cannot set a frame with no "
                                                 "defined index and a scalar")
                            self.obj[key] = value
                            return self.obj

                        self.obj[key] = np.nan

                        new_indexer = _convert_from_missing_indexer_tuple(
                            indexer, self.obj.axes)
                        self._setitem_with_indexer(new_indexer, value)
                        return self.obj

                    # reindex the axis
                    # make sure to clear the cache because we are
                    # just replacing the block manager here
                    # so the object is the same
                    index = self.obj._get_axis(i)
                    labels = _safe_append_to_index(index, key)
                    self.obj._data = self.obj.reindex_axis(labels, i)._data
                    self.obj._maybe_update_cacher(clear=True)
                    self.obj.is_copy=None

                    if isinstance(labels, MultiIndex):
                        self.obj.sortlevel(inplace=True)
                        labels = self.obj._get_axis(i)

                    nindexer.append(labels.get_loc(key))

                else:
                    nindexer.append(idx)

            indexer = tuple(nindexer)
        else:

            indexer, missing = _convert_missing_indexer(indexer)

            if missing:

                # reindex the axis to the new value
                # and set inplace
                if self.ndim == 1:
                    index = self.obj.index
                    if len(index) == 0:
                        new_index = Index([indexer])
                    else:
                        new_index = _safe_append_to_index(index, indexer)

                    # this preserves dtype of the value
                    new_values = Series([value]).values
                    if len(self.obj.values):
                        new_values = np.concatenate([self.obj.values,
                                                     new_values])

                    self.obj._data = self.obj._constructor(
                        new_values, index=new_index, name=self.obj.name)._data
                    self.obj._maybe_update_cacher(clear=True)
                    return self.obj

                elif self.ndim == 2:

                    # no columns and scalar
                    if not len(self.obj.columns):
                        raise ValueError(
                            "cannot set a frame with no defined columns"
                        )

                    index = self.obj._get_axis(0)
                    labels = _safe_append_to_index(index, indexer)
                    self.obj._data = self.obj.reindex_axis(labels, 0)._data
                    self.obj._maybe_update_cacher(clear=True)
                    return getattr(self.obj, self.name).__setitem__(indexer,
                                                                    value)

                # set using setitem (Panel and > dims)
                elif self.ndim >= 3:
                    return self.obj.__setitem__(indexer, value)

        # set
        info_axis = self.obj._info_axis_number
        item_labels = self.obj._get_axis(info_axis)

        # if we have a complicated setup, take the split path
        if (isinstance(indexer, tuple) and
                any([isinstance(ax, MultiIndex) for ax in self.obj.axes])):
            take_split_path = True

        # align and set the values
        if take_split_path:

            if not isinstance(indexer, tuple):
                indexer = self._tuplify(indexer)

            if isinstance(value, ABCSeries):
                value = self._align_series(indexer, value)

            info_idx = indexer[info_axis]
            if com.is_integer(info_idx):
                info_idx = [info_idx]
            labels = item_labels[info_idx]

            # if we have a partial multiindex, then need to adjust the plane
            # indexer here
            if (len(labels) == 1 and
                    isinstance(self.obj[labels[0]].index, MultiIndex)):
                item = labels[0]
                obj = self.obj[item]
                index = obj.index
                idx = indexer[:info_axis][0]
                try:
                    if idx in index:
                        idx = index.get_loc(idx)
                except:
                    pass
                plane_indexer = tuple([idx]) + indexer[info_axis + 1:]
                lplane_indexer = _length_of_indexer(plane_indexer[0], index)

                # require that we are setting the right number of values that
                # we are indexing
                if is_list_like(value) and lplane_indexer != len(value):

                    if len(obj[idx]) != len(value):
                        raise ValueError(
                            "cannot set using a multi-index selection indexer "
                            "with a different length than the value"
                        )

                    # we can directly set the series here
                    # as we select a slice indexer on the mi
                    idx = index._convert_slice_indexer(idx)
                    obj = obj.copy()
                    obj._data = obj._data.setitem(indexer=tuple([idx]), value=value)
                    self.obj[item] = obj
                    return

            # non-mi
            else:
                plane_indexer = indexer[:info_axis] + indexer[info_axis + 1:]
                if info_axis > 0:
                    plane_axis = self.obj.axes[:info_axis][0]
                    lplane_indexer = _length_of_indexer(plane_indexer[0],
                                                        plane_axis)
                else:
                    lplane_indexer = 0

            def setter(item, v):
                s = self.obj[item]
                pi = plane_indexer[0] if lplane_indexer == 1 else plane_indexer

                # perform the equivalent of a setitem on the info axis
                # as we have a null slice which means essentially reassign to the columns
                # of a multi-dim object
                # GH6149
                if isinstance(pi, tuple) and all(_is_null_slice(idx) for idx in pi):
                    s = v
                else:
                    # set the item, possibly having a dtype change
                    s = s.copy()
                    s._data = s._data.setitem(indexer=pi, value=v)
                    s._maybe_update_cacher(clear=True)

                self.obj[item] = s

            def can_do_equal_len():
                """ return True if we have an equal len settable """
                if not len(labels) == 1:
                    return False

                l = len(value)
                item = labels[0]
                index = self.obj[item].index

                # equal len list/ndarray
                if len(index) == l:
                    return True
                elif lplane_indexer == l:
                    return True

                return False

            if _is_list_like(value):

                # we have an equal len Frame
                if isinstance(value, ABCDataFrame) and value.ndim > 1:

                    for item in labels:

                        # align to
                        if item in value:
                            v = value[item]
                            i = self.obj[item].index
                            v = v.reindex(i & v.index)

                            setter(item, v.values)
                        else:
                            setter(item, np.nan)

                # we have an equal len ndarray to our labels
                elif isinstance(value, np.ndarray) and value.ndim == 2:
                    if len(labels) != value.shape[1]:
                        raise ValueError('Must have equal len keys and value '
                                         'when setting with an ndarray')

                    for i, item in enumerate(labels):
                        setter(item, value[:, i])

                # we have an equal len list/ndarray
                elif can_do_equal_len():
                    setter(labels[0], value)

                # per label values
                else:

                    if len(labels) != len(value):
                        raise ValueError('Must have equal len keys and value'
                                         'when setting with an iterable')

                    for item, v in zip(labels, value):
                        setter(item, v)
            else:

                # scalar
                for item in labels:
                    setter(item, value)

        else:
            if isinstance(indexer, tuple):
                indexer = _maybe_convert_ix(*indexer)

            if isinstance(value, ABCSeries):
                value = self._align_series(indexer, value)

            elif isinstance(value, ABCDataFrame):
                value = self._align_frame(indexer, value)

            if isinstance(value, ABCPanel):
                value = self._align_panel(indexer, value)

            # actually do the set
            self.obj._data = self.obj._data.setitem(indexer=indexer, value=value)
            self.obj._maybe_update_cacher(clear=True)

    def _align_series(self, indexer, ser):
        # indexer to assign Series can be tuple, slice, scalar
        if isinstance(indexer, (slice, np.ndarray, list)):
            indexer = tuple([indexer])

        if isinstance(indexer, tuple):

            aligners = [not _is_null_slice(idx) for idx in indexer]
            sum_aligners = sum(aligners)
            single_aligner = sum_aligners == 1
            is_frame = self.obj.ndim == 2
            is_panel = self.obj.ndim >= 3
            obj = self.obj

            # are we a single alignable value on a non-primary
            # dim (e.g. panel: 1,2, or frame: 0) ?
            # hence need to align to a single axis dimension
            # rather that find all valid dims

            # frame
            if is_frame:
                single_aligner = single_aligner and aligners[0]

            # panel
            elif is_panel:
                single_aligner = (single_aligner and
                                  (aligners[1] or aligners[2]))

            # we have a frame, with multiple indexers on both axes; and a
            # series, so need to broadcast (see GH5206)
            if (sum_aligners == self.ndim and
                    all([com._is_sequence(_) for _ in indexer])):
                ser = ser.reindex(obj.axes[0][indexer[0].ravel()],
                                  copy=True).values

                # single indexer
                if len(indexer) > 1:
                    l = len(indexer[1].ravel())
                    ser = np.tile(ser, l).reshape(l, -1).T

                return ser

            for i, idx in enumerate(indexer):
                ax = obj.axes[i]

                # multiple aligners (or null slices)
                if com._is_sequence(idx) or isinstance(idx, slice):
                    if single_aligner and _is_null_slice(idx):
                        continue
                    new_ix = ax[idx]
                    if not is_list_like(new_ix):
                        new_ix = Index([new_ix])
                    else:
                        new_ix = Index(new_ix.ravel())
                    if ser.index.equals(new_ix) or not len(new_ix):
                        return ser.values.copy()

                    return ser.reindex(new_ix).values

                # 2 dims
                elif single_aligner and is_frame:

                    # reindex along index
                    ax = self.obj.axes[1]
                    if ser.index.equals(ax) or not len(ax):
                        return ser.values.copy()
                    return ser.reindex(ax).values

                # >2 dims
                elif single_aligner:

                    broadcast = []
                    for n, labels in enumerate(self.obj._get_plane_axes(i)):

                        # reindex along the matching dimensions
                        if len(labels & ser.index):
                            ser = ser.reindex(labels)
                        else:
                            broadcast.append((n, len(labels)))

                    # broadcast along other dims
                    ser = ser.values.copy()
                    for (axis, l) in broadcast:
                        shape = [-1] * (len(broadcast) + 1)
                        shape[axis] = l
                        ser = np.tile(ser, l).reshape(shape)

                    if self.obj.ndim == 3:
                        ser = ser.T

                    return ser

        elif np.isscalar(indexer):
            ax = self.obj._get_axis(1)

            if ser.index.equals(ax):
                return ser.values.copy()

            return ser.reindex(ax).values

        raise ValueError('Incompatible indexer with Series')

    def _align_frame(self, indexer, df):
        is_frame = self.obj.ndim == 2
        is_panel = self.obj.ndim >= 3
        if isinstance(indexer, tuple):
            idx, cols = None, None
            sindexers = []
            for i, ix in enumerate(indexer):
                ax = self.obj.axes[i]
                if com._is_sequence(ix) or isinstance(ix, slice):
                    if idx is None:
                        idx = ax[ix].ravel()
                    elif cols is None:
                        cols = ax[ix].ravel()
                    else:
                        break
                else:
                    sindexers.append(i)

            # panel
            if is_panel:
                if len(sindexers) == 1 and idx is None and cols is None:
                    if sindexers[0] == 0:
                        df = df.T
                    return self.obj.conform(df, axis=sindexers[0])
                df = df.T

            if idx is not None and cols is not None:
                if df.index.equals(idx) and df.columns.equals(cols):
                    val = df.copy().values
                else:
                    val = df.reindex(idx, columns=cols).values
                return val

        elif ((isinstance(indexer, slice) or com.is_list_like(indexer))
              and is_frame):
            ax = self.obj.index[indexer]
            if df.index.equals(ax):
                val = df.copy().values
            else:

                # we have a multi-index and are trying to align
                # with a particular, level GH3738
                if isinstance(ax, MultiIndex) and isinstance(
                    df.index, MultiIndex) and ax.nlevels != df.index.nlevels:
                    raise TypeError("cannot align on a multi-index with out specifying the join levels")

                val = df.reindex(index=ax).values
            return val

        elif np.isscalar(indexer) and not is_frame:
            idx = self.obj.axes[1]
            cols = self.obj.axes[2]

            # by definition we are indexing on the 0th axis
            if is_panel:
                df = df.T

            if idx.equals(df.index) and cols.equals(df.columns):
                return df.copy().values

            # a passed in dataframe which is actually a transpose
            # of what is needed
            elif idx.equals(df.columns) and cols.equals(df.index):
                return df.T.copy().values

            return df.reindex(idx, columns=cols).values

        raise ValueError('Incompatible indexer with DataFrame')

    def _align_panel(self, indexer, df):
        is_frame = self.obj.ndim == 2
        is_panel = self.obj.ndim >= 3
        raise NotImplementedError("cannot set using an indexer with a Panel "
                                  "yet!")

    def _getitem_tuple(self, tup):
        try:
            return self._getitem_lowerdim(tup)
        except IndexingError:
            pass

        # no multi-index, so validate all of the indexers
        self._has_valid_tuple(tup)

        # ugly hack for GH #836
        if self._multi_take_opportunity(tup):
            return self._multi_take(tup)

        # no shortcut needed
        retval = self.obj
        for i, key in enumerate(tup):
            if i >= self.obj.ndim:
                raise IndexingError('Too many indexers')

            if _is_null_slice(key):
                continue

            retval = getattr(retval, self.name)._getitem_axis(key, axis=i)

        return retval

    def _multi_take_opportunity(self, tup):
        from pandas.core.generic import NDFrame

        # ugly hack for GH #836
        if not isinstance(self.obj, NDFrame):
            return False

        if not all(_is_list_like(x) for x in tup):
            return False

        # just too complicated
        for indexer, ax in zip(tup, self.obj._data.axes):
            if isinstance(ax, MultiIndex):
                return False
            elif com._is_bool_indexer(indexer):
                return False
            elif not ax.is_unique:
                return False

        return True

    def _multi_take(self, tup):
        """ create the reindex map for our objects, raise the _exception if we
        can't create the indexer
        """
        try:
            o = self.obj
            d = dict([
                (a, self._convert_for_reindex(t, axis=o._get_axis_number(a)))
                for t, a in zip(tup, o._AXIS_ORDERS)
            ])
            return o.reindex(**d)
        except:
            raise self._exception

    def _convert_for_reindex(self, key, axis=0):
        labels = self.obj._get_axis(axis)

        if com._is_bool_indexer(key):
            key = _check_bool_indexer(labels, key)
            return labels[key]
        else:
            if isinstance(key, Index):
                # want Index objects to pass through untouched
                keyarr = key
            else:
                # asarray can be unsafe, NumPy strings are weird
                keyarr = _asarray_tuplesafe(key)

            if is_integer_dtype(keyarr) and not labels.is_integer():
                keyarr = com._ensure_platform_int(keyarr)
                return labels.take(keyarr)

            return keyarr

    def _handle_lowerdim_multi_index_axis0(self, tup):
        # we have an axis0 multi-index, handle or raise

        try:
            # fast path for series or for tup devoid of slices
            return self._get_label(tup, axis=0)
        except TypeError:
            # slices are unhashable
            pass
        except Exception as e1:
            if isinstance(tup[0], (slice, Index)):
                raise IndexingError("Handle elsewhere")

            # raise the error if we are not sorted
            ax0 = self.obj._get_axis(0)
            if not ax0.is_lexsorted_for_tuple(tup):
                raise e1

        return None

    def _getitem_lowerdim(self, tup):

        # we can directly get the axis result since the axis is specified
        if self.axis is not None:
            axis = self.obj._get_axis_number(self.axis)
            return self._getitem_axis(tup, axis=axis, validate_iterable=True)

        # we may have a nested tuples indexer here
        if self._is_nested_tuple_indexer(tup):
            return self._getitem_nested_tuple(tup)

        # we maybe be using a tuple to represent multiple dimensions here
        ax0 = self.obj._get_axis(0)
        if isinstance(ax0, MultiIndex):
            result = self._handle_lowerdim_multi_index_axis0(tup)
            if result is not None:
                return result

        if len(tup) > self.obj.ndim:
            raise IndexingError("Too many indexers. handle elsewhere")

        # to avoid wasted computation
        # df.ix[d1:d2, 0] -> columns first (True)
        # df.ix[0, ['C', 'B', A']] -> rows first (False)
        for i, key in enumerate(tup):
            if _is_label_like(key) or isinstance(key, tuple):
                section = self._getitem_axis(key, axis=i)

                # we have yielded a scalar ?
                if not _is_list_like(section):
                    return section

                elif section.ndim == self.ndim:
                    # we're in the middle of slicing through a MultiIndex
                    # revise the key wrt to `section` by inserting an _NS
                    new_key = tup[:i] + (_NS,) + tup[i + 1:]

                else:
                    new_key = tup[:i] + tup[i + 1:]

                    # unfortunately need an odious kludge here because of
                    # DataFrame transposing convention
                    if (isinstance(section, ABCDataFrame) and i > 0
                            and len(new_key) == 2):
                        a, b = new_key
                        new_key = b, a

                    if len(new_key) == 1:
                        new_key, = new_key

                # This is an elided recursive call to iloc/loc/etc'
                return getattr(section, self.name)[new_key]

        raise IndexingError('not applicable')

    def _getitem_nested_tuple(self, tup):
        # we have a nested tuple so have at least 1 multi-index level
        # we should be able to match up the dimensionaility here

        # we have too many indexers for our dim, but have at least 1
        # multi-index dimension, try to see if we have something like
        # a tuple passed to a series with a multi-index
        if len(tup) > self.ndim:
            result = self._handle_lowerdim_multi_index_axis0(tup)
            if result is not None:
                return result

            # this is a series with a multi-index specified a tuple of selectors
            return self._getitem_axis(tup, axis=0, validate_iterable=True)

        # handle the multi-axis by taking sections and reducing
        # this is iterative
        obj = self.obj
        axis = 0
        for key in tup:

            if _is_null_slice(key):
                axis += 1
                continue

            obj = getattr(obj, self.name)._getitem_axis(key, axis=axis, validate_iterable=True)
            axis += 1

            if obj.ndim < self.ndim:
                axis -= 1

        return obj

    def _getitem_axis(self, key, axis=0, validate_iterable=False):

        self._has_valid_type(key, axis)
        labels = self.obj._get_axis(axis)
        if isinstance(key, slice):
            return self._get_slice_axis(key, axis=axis)
        elif _is_list_like(key) and not (isinstance(key, tuple) and
                                         isinstance(labels, MultiIndex)):

            if hasattr(key, 'ndim') and key.ndim > 1:
                raise ValueError('Cannot index with multidimensional key')

            return self._getitem_iterable(key, axis=axis)
        else:
            if com.is_integer(key):
                if axis == 0 and isinstance(labels, MultiIndex):
                    try:
                        return self._get_label(key, axis=axis)
                    except (KeyError, TypeError):
                        if self.obj.index.levels[0].is_integer():
                            raise

                # this is the fallback! (for a non-float, non-integer index)
                if not labels.is_floating() and not labels.is_integer():
                    return self._get_loc(key, axis=axis)

            return self._get_label(key, axis=axis)

    def _getitem_iterable(self, key, axis=0):
        labels = self.obj._get_axis(axis)

        def _reindex(keys, level=None):
            try:
                return self.obj.reindex_axis(keys, axis=axis, level=level)
            except AttributeError:
                # Series
                if axis != 0:
                    raise AssertionError('axis must be 0')
                return self.obj.reindex(keys, level=level)

        if com._is_bool_indexer(key):
            key = _check_bool_indexer(labels, key)
            inds, = key.nonzero()
            return self.obj.take(inds, axis=axis, convert=False)
        else:
            if isinstance(key, Index):
                # want Index objects to pass through untouched
                keyarr = key
            else:
                # asarray can be unsafe, NumPy strings are weird
                keyarr = _asarray_tuplesafe(key)

            # handle a mixed integer scenario
            indexer = labels._convert_list_indexer_for_mixed(keyarr, typ=self.name)
            if indexer is not None:
                return self.obj.take(indexer, axis=axis)

            # this is not the most robust, but...
            if (isinstance(labels, MultiIndex) and
                    not isinstance(keyarr[0], tuple)):
                level = 0
            else:
                level = None

            keyarr_is_unique = Index(keyarr).is_unique

            # existing labels are unique and indexer is unique
            if labels.is_unique and keyarr_is_unique:
                return _reindex(keyarr, level=level)

            else:
                indexer, missing = labels.get_indexer_non_unique(keyarr)
                check = indexer != -1
                result = self.obj.take(indexer[check], axis=axis,
                                       convert=False)

                # need to merge the result labels and the missing labels
                if len(missing):
                    l = np.arange(len(indexer))

                    missing = com._ensure_platform_int(missing)
                    missing_labels = keyarr.take(missing)
                    missing_indexer = com._ensure_int64(l[~check])
                    cur_labels = result._get_axis(axis).values
                    cur_indexer = com._ensure_int64(l[check])

                    new_labels = np.empty(tuple([len(indexer)]), dtype=object)
                    new_labels[cur_indexer] = cur_labels
                    new_labels[missing_indexer] = missing_labels

                    # reindex with the specified axis
                    ndim = self.obj.ndim
                    if axis + 1 > ndim:
                        raise AssertionError("invalid indexing error with "
                                             "non-unique index")

                    # a unique indexer
                    if keyarr_is_unique:

                        # see GH5553, make sure we use the right indexer
                        new_indexer = np.arange(len(indexer))
                        new_indexer[cur_indexer] = np.arange(
                            len(result._get_axis(axis))
                        )
                        new_indexer[missing_indexer] = -1

                    # we have a non_unique selector, need to use the original
                    # indexer here
                    else:

                        # need to retake to have the same size as the indexer
                        rindexer = indexer.values
                        rindexer[~check] = 0
                        result = self.obj.take(rindexer, axis=axis,
                                               convert=False)

                        # reset the new indexer to account for the new size
                        new_indexer = np.arange(len(result))
                        new_indexer[~check] = -1

                    result = result._reindex_with_indexers({
                        axis: [new_labels, new_indexer]
                    }, copy=True, allow_dups=True)

                return result

    def _convert_to_indexer(self, obj, axis=0, is_setter=False):
        """
        Convert indexing key into something we can use to do actual fancy
        indexing on an ndarray

        Examples
        ix[:5] -> slice(0, 5)
        ix[[1,2,3]] -> [1,2,3]
        ix[['foo', 'bar', 'baz']] -> [i, j, k] (indices of foo, bar, baz)

        Going by Zen of Python?
        "In the face of ambiguity, refuse the temptation to guess."
        raise AmbiguousIndexError with integer labels?
        - No, prefer label-based indexing
        """
        labels = self.obj._get_axis(axis)

        # if we are a scalar indexer and not type correct raise
        obj = self._convert_scalar_indexer(obj, axis)

        # see if we are positional in nature
        is_int_index = labels.is_integer()
        is_int_positional = com.is_integer(obj) and not is_int_index

        # if we are a label return me
        try:
            return labels.get_loc(obj)
        except (KeyError, TypeError):
            pass
        except (ValueError):
            if not is_int_positional:
                raise

        # a positional
        if is_int_positional:

            # if we are setting and its not a valid location
            # its an insert which fails by definition
            if is_setter:

                # always valid
                if self.name == 'loc':
                    return {'key': obj}

                # a positional
                if (obj >= self.obj.shape[axis] and
                        not isinstance(labels, MultiIndex)):
                    raise ValueError("cannot set by positional indexing with "
                                     "enlargement")

            return obj

        if isinstance(obj, slice):
            return self._convert_slice_indexer(obj, axis)

        elif _is_nested_tuple(obj, labels):
            return labels.get_locs(obj)
        elif _is_list_like(obj):
            if com._is_bool_indexer(obj):
                obj = _check_bool_indexer(labels, obj)
                inds, = obj.nonzero()
                return inds
            else:
                if isinstance(obj, Index):
                    objarr = obj.values
                else:
                    objarr = _asarray_tuplesafe(obj)

                # If have integer labels, defer to label-based indexing
                indexer = labels._convert_list_indexer_for_mixed(objarr, typ=self.name)
                if indexer is not None:
                    return indexer

                # this is not the most robust, but...
                if (isinstance(labels, MultiIndex) and
                        not isinstance(objarr[0], tuple)):
                    level = 0
                    _, indexer = labels.reindex(objarr, level=level)

                    check = labels.levels[0].get_indexer(objarr)
                else:
                    level = None

                    # unique index
                    if labels.is_unique:
                        indexer = check = labels.get_indexer(objarr)

                    # non-unique (dups)
                    else:
                        (indexer,
                         missing) = labels.get_indexer_non_unique(objarr)
                        check = indexer

                mask = check == -1
                if mask.any():

                    # mi here
                    if isinstance(obj, tuple) and is_setter:
                        return {'key': obj}
                    raise KeyError('%s not in index' % objarr[mask])

                return indexer

        else:
            try:
                return labels.get_loc(obj)
            except KeyError:
                # allow a not found key only if we are a setter
                if not is_list_like(obj) and is_setter:
                    return {'key': obj}
                raise

    def _tuplify(self, loc):
        tup = [slice(None, None) for _ in range(self.ndim)]
        tup[0] = loc
        return tuple(tup)

    def _get_slice_axis(self, slice_obj, axis=0):
        obj = self.obj

        if not _need_slice(slice_obj):
            return obj
        indexer = self._convert_slice_indexer(slice_obj, axis)

        if isinstance(indexer, slice):
            return self._slice(indexer, axis=axis, typ='iloc')
        else:
            return self.obj.take(indexer, axis=axis, convert=False)


class _IXIndexer(_NDFrameIndexer):

    """ A primarily location based indexer, with integer fallback """

    def _has_valid_type(self, key, axis):
        ax = self.obj._get_axis(axis)

        if isinstance(key, slice):
            return True

        elif com._is_bool_indexer(key):
            return True

        elif _is_list_like(key):
            return True

        else:

            self._convert_scalar_indexer(key, axis)

        return True


class _LocationIndexer(_NDFrameIndexer):
    _exception = Exception

    def __getitem__(self, key):
        if type(key) is tuple:
            return self._getitem_tuple(key)
        else:
            return self._getitem_axis(key, axis=0)

    def _getitem_axis(self, key, axis=0, validate_iterable=False):
        raise NotImplementedError()

    def _getbool_axis(self, key, axis=0):
            labels = self.obj._get_axis(axis)
            key = _check_bool_indexer(labels, key)
            inds, = key.nonzero()
            try:
                return self.obj.take(inds, axis=axis, convert=False)
            except Exception as detail:
                raise self._exception(detail)

    def _get_slice_axis(self, slice_obj, axis=0):
        """ this is pretty simple as we just have to deal with labels """
        obj = self.obj
        if not _need_slice(slice_obj):
            return obj

        labels = obj._get_axis(axis)
        indexer = labels.slice_indexer(slice_obj.start, slice_obj.stop,
                                       slice_obj.step)

        if isinstance(indexer, slice):
            return self._slice(indexer, axis=axis, typ='iloc')
        else:
            return self.obj.take(indexer, axis=axis, convert=False)


class _LocIndexer(_LocationIndexer):

    """ purely label based location based indexing """
    _valid_types = ("labels (MUST BE IN THE INDEX), slices of labels (BOTH "
                    "endpoints included! Can be slices of integers if the "
                    "index is integers), listlike of labels, boolean")
    _exception = KeyError

    def _has_valid_type(self, key, axis):
        ax = self.obj._get_axis(axis)

        # valid for a label where all labels are in the index
        # slice of lables (where start-end in labels)
        # slice of integers (only if in the lables)
        # boolean

        if isinstance(key, slice):

            if ax.is_floating():

                # allowing keys to be slicers with no fallback
                pass

            else:
                if key.start is not None:
                    if key.start not in ax:
                        raise KeyError(
                            "start bound [%s] is not the [%s]" %
                            (key.start, self.obj._get_axis_name(axis))
                        )
                if key.stop is not None:
                    if key.stop not in ax:
                        raise KeyError(
                            "stop bound [%s] is not in the [%s]" %
                            (key.stop, self.obj._get_axis_name(axis))
                        )

        elif com._is_bool_indexer(key):
                return True

        elif _is_list_like(key):

            # mi is just a passthru
            if isinstance(key, tuple) and isinstance(ax, MultiIndex):
                return True

            # require all elements in the index
            idx = _ensure_index(key)
            if not idx.isin(ax).all():

                raise KeyError("[%s] are not in ALL in the [%s]" %
                               (key, self.obj._get_axis_name(axis)))

            return True

        else:

            def error():
                if isnull(key):
                    raise ValueError(
                        "cannot use label indexing with a null key")
                raise KeyError("the label [%s] is not in the [%s]" %
                               (key, self.obj._get_axis_name(axis)))

            try:
                key = self._convert_scalar_indexer(key, axis)
                if not key in ax:
                    error()
            except (TypeError) as e:

                # python 3 type errors should be raised
                if 'unorderable' in str(e):  # pragma: no cover
                    error()
                raise
            except:
                error()

        return True

    def _getitem_axis(self, key, axis=0, validate_iterable=False):
        labels = self.obj._get_axis(axis)

        if isinstance(key, slice):
            self._has_valid_type(key, axis)
            return self._get_slice_axis(key, axis=axis)
        elif com._is_bool_indexer(key):
            return self._getbool_axis(key, axis=axis)
        elif _is_list_like(key) and not (isinstance(key, tuple) and
                                         isinstance(labels, MultiIndex)):

            if hasattr(key, 'ndim') and key.ndim > 1:
                raise ValueError('Cannot index with multidimensional key')

            if validate_iterable:
                self._has_valid_type(key, axis)
            return self._getitem_iterable(key, axis=axis)
        elif _is_nested_tuple(key, labels):
            locs = labels.get_locs(key)
            indexer = [ slice(None) ] * self.ndim
            indexer[axis] = locs
            return self.obj.iloc[tuple(indexer)]
        else:
            self._has_valid_type(key, axis)
            return self._get_label(key, axis=axis)


class _iLocIndexer(_LocationIndexer):

    """ purely integer based location based indexing """
    _valid_types = ("integer, integer slice (START point is INCLUDED, END "
                    "point is EXCLUDED), listlike of integers, boolean array")
    _exception = IndexError

    def _has_valid_type(self, key, axis):
        if com._is_bool_indexer(key):
            if hasattr(key, 'index') and isinstance(key.index, Index):
                if key.index.inferred_type == 'integer':
                    raise NotImplementedError(
                        "iLocation based boolean indexing on an integer type "
                        "is not available"
                    )
                raise ValueError("iLocation based boolean indexing cannot use "
                                 "an indexable as a mask")
            return True

        return (isinstance(key, slice) or
                com.is_integer(key) or
                _is_list_like(key))

    def _has_valid_setitem_indexer(self, indexer):
        self._has_valid_positional_setitem_indexer(indexer)

    def _getitem_tuple(self, tup):

        self._has_valid_tuple(tup)
        try:
            return self._getitem_lowerdim(tup)
        except:
            pass

        retval = self.obj
        axis=0
        for i, key in enumerate(tup):
            if i >= self.obj.ndim:
                raise IndexingError('Too many indexers')

            if _is_null_slice(key):
                axis += 1
                continue

            retval = getattr(retval, self.name)._getitem_axis(key, axis=axis)

            # if the dim was reduced, then pass a lower-dim the next time
            if retval.ndim<self.ndim:
                axis -= 1

            # try to get for the next axis
            axis += 1

        return retval

    def _get_slice_axis(self, slice_obj, axis=0):
        obj = self.obj

        if not _need_slice(slice_obj):
            return obj

        if isinstance(slice_obj, slice):
            return self._slice(slice_obj, axis=axis, raise_on_error=True,
                               typ='iloc')
        else:
            return self.obj.take(slice_obj, axis=axis, convert=False)

    def _getitem_axis(self, key, axis=0, validate_iterable=False):

        if isinstance(key, slice):
            self._has_valid_type(key, axis)
            return self._get_slice_axis(key, axis=axis)

        elif com._is_bool_indexer(key):
            self._has_valid_type(key, axis)
            return self._getbool_axis(key, axis=axis)

        # a single integer or a list of integers
        else:

            ax = self.obj._get_axis(axis)
            if _is_list_like(key):

                # coerce the key to not exceed the maximum size of the index
                arr = np.array(key)
                l = len(ax)
                if len(arr) and (arr.max() >= l or arr.min() <= -l):
                    raise IndexError("positional indexers are out-of-bounds")

                # force an actual list
                key = list(key)

            else:
                key = self._convert_scalar_indexer(key, axis)

                if not com.is_integer(key):
                    raise TypeError("Cannot index by location index with a "
                                    "non-integer key")

                if key > len(ax):
                    raise IndexError("single positional indexer is out-of-bounds")

            return self._get_loc(key, axis=axis)

    def _convert_to_indexer(self, obj, axis=0, is_setter=False):
        """ much simpler as we only have to deal with our valid types """
        if self._has_valid_type(obj, axis):
            return obj

        raise ValueError("Can only index by location with a [%s]" %
                         self._valid_types)


class _ScalarAccessIndexer(_NDFrameIndexer):

    """ access scalars quickly """

    def _convert_key(self, key):
        return list(key)

    def __getitem__(self, key):
        if not isinstance(key, tuple):

            # we could have a convertible item here (e.g. Timestamp)
            if not _is_list_like(key):
                key = tuple([key])
            else:
                raise ValueError('Invalid call for scalar access (getting)!')

        key = self._convert_key(key)
        return self.obj.get_value(*key, takeable=self._takeable)

    def __setitem__(self, key, value):
        if not isinstance(key, tuple):
            key = self._tuplify(key)
        if len(key) != self.obj.ndim:
            raise ValueError('Not enough indexers for scalar access '
                             '(setting)!')
        key = list(self._convert_key(key))
        key.append(value)
        self.obj.set_value(*key, takeable=self._takeable)


class _AtIndexer(_ScalarAccessIndexer):

    """ label based scalar accessor """
    _takeable = False


class _iAtIndexer(_ScalarAccessIndexer):

    """ integer based scalar accessor """
    _takeable = True

    def _has_valid_setitem_indexer(self, indexer):
        self._has_valid_positional_setitem_indexer(indexer)

    def _convert_key(self, key):
        """ require  integer args (and convert to label arguments) """
        for a, i in zip(self.obj.axes, key):
            if not com.is_integer(i):
                raise ValueError("iAt based indexing can only have integer "
                                 "indexers")
        return key

# 32-bit floating point machine epsilon
_eps = np.finfo('f4').eps


def _length_of_indexer(indexer, target=None):
    """return the length of a single non-tuple indexer which could be a slice
    """
    if target is not None and isinstance(indexer, slice):
        l = len(target)
        start = indexer.start
        stop = indexer.stop
        step = indexer.step
        if start is None:
            start = 0
        elif start < 0:
            start += l
        if stop is None or stop > l:
            stop = l
        elif stop < 0:
            stop += l
        if step is None:
            step = 1
        elif step < 0:
            step = abs(step)
        return (stop - start) / step
    elif isinstance(indexer, (ABCSeries, np.ndarray, list)):
        return len(indexer)
    elif not is_list_like(indexer):
        return 1
    raise AssertionError("cannot find the length of the indexer")


def _convert_to_index_sliceable(obj, key):
    """if we are index sliceable, then return my slicer, otherwise return None
    """
    idx = obj.index
    if isinstance(key, slice):
        return idx._convert_slice_indexer(key, typ='getitem')

    elif isinstance(key, compat.string_types):

        # we are an actual column
        if key in obj._data.items:
            return None

        # we need a timelike key here
        if idx.is_all_dates:
            try:
                return idx._get_string_slice(key)
            except:
                return None

    return None


def _is_index_slice(obj):
    def _is_valid_index(x):
        return (com.is_integer(x) or com.is_float(x)
                and np.allclose(x, int(x), rtol=_eps, atol=0))

    def _crit(v):
        return v is None or _is_valid_index(v)

    both_none = obj.start is None and obj.stop is None

    return not both_none and (_crit(obj.start) and _crit(obj.stop))


def _check_bool_indexer(ax, key):
    # boolean indexing, need to check that the data are aligned, otherwise
    # disallowed

    # this function assumes that com._is_bool_indexer(key) == True

    result = key
    if isinstance(key, ABCSeries) and not key.index.equals(ax):
        result = result.reindex(ax)
        mask = com.isnull(result.values)
        if mask.any():
            raise IndexingError('Unalignable boolean Series key provided')

        result = result.astype(bool).values

    else:
        # com._is_bool_indexer has already checked for nulls in the case of an
        # object array key, so no check needed here
        result = np.asarray(result, dtype=bool)

    return result


def _convert_missing_indexer(indexer):
    """ reverse convert a missing indexer, which is a dict
        return the scalar indexer and a boolean indicating if we converted """

    if isinstance(indexer, dict):

        # a missing key (but not a tuple indexer)
        indexer = indexer['key']

        if isinstance(indexer, bool):
            raise KeyError("cannot use a single bool to index into setitem")
        return indexer, True

    return indexer, False


def _convert_from_missing_indexer_tuple(indexer, axes):
    """ create a filtered indexer that doesn't have any missing indexers """
    def get_indexer(_i, _idx):
        return (axes[_i].get_loc(_idx['key'])
                if isinstance(_idx, dict) else _idx)
    return tuple([get_indexer(_i, _idx) for _i, _idx in enumerate(indexer)])


def _safe_append_to_index(index, key):
    """ a safe append to an index, if incorrect type, then catch and recreate
    """
    try:
        return index.insert(len(index), key)
    except:

        # raise here as this is basically an unsafe operation and we want
        # it to be obvious that you are doing something wrong
        raise ValueError("unsafe appending to index of type {0} with a key "
                         "{1}".format(index.__class__.__name__, key))


def _maybe_convert_indices(indices, n):
    """ if we have negative indicies, translate to postive here
    if have indicies that are out-of-bounds, raise an IndexError
    """
    if isinstance(indices, list):
        indices = np.array(indices)

    mask = indices < 0
    if mask.any():
        indices[mask] += n
    mask = (indices >= n) | (indices < 0)
    if mask.any():
        raise IndexError("indices are out-of-bounds")
    return indices


def _maybe_convert_ix(*args):
    """
    We likely want to take the cross-product
    """

    ixify = True
    for arg in args:
        if not isinstance(arg, (np.ndarray, list, ABCSeries)):
            ixify = False

    if ixify:
        return np.ix_(*args)
    else:
        return args


def _is_nested_tuple(tup, labels):
    # check for a compatiable nested tuple and multiindexes among the axes

    if not isinstance(tup, tuple):
        return False

    # are we nested tuple of: tuple,list,slice
    for i, k in enumerate(tup):

        #if i > len(axes):
        #    raise IndexingError("invalid indxing tuple passed, has too many indexers for this object")
        #ax = axes[i]
        if isinstance(k, (tuple, list, slice)):
            return isinstance(labels, MultiIndex)

    return False


def _is_null_slice(obj):
    return (isinstance(obj, slice) and obj.start is None and
            obj.stop is None and obj.step is None)


def _is_label_like(key):
    # select a label or row
    return not isinstance(key, slice) and not _is_list_like(key)


def _is_list_like(obj):
    # Consider namedtuples to be not list like as they are useful as indices
    return (np.iterable(obj)
            and not isinstance(obj, compat.string_types)
            and not (isinstance(obj, tuple) and type(obj) is not tuple))


def _need_slice(obj):
    return (obj.start is not None or
            obj.stop is not None or
            (obj.step is not None and obj.step != 1))


def _check_slice_bounds(slobj, values):
    l = len(values)
    start = slobj.start
    if start is not None:
        if start < -l or start > l - 1:
            raise IndexError("out-of-bounds on slice (start)")
    stop = slobj.stop
    if stop is not None:
        if stop < -l - 1 or stop > l:
            raise IndexError("out-of-bounds on slice (end)")


def _maybe_droplevels(index, key):
    # drop levels
    original_index = index
    if isinstance(key, tuple):
        for _ in key:
            try:
                index = index.droplevel(0)
            except:
                # we have dropped too much, so back out
                return original_index
    else:
        try:
            index = index.droplevel(0)
        except:
            pass

    return index