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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>matplotlib.legend — Matplotlib 3.1.1 documentation</title>

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<div style="float: left; position: absolute; width: 496px; bottom: 0; padding-bottom: 24px">Version 3.1.1</div>

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<h1>Source code for matplotlib.legend</h1><div class="highlight"><pre>

"""

The legend module defines the Legend class, which is responsible for

drawing legends associated with axes and/or figures.

.. important::

It is unlikely that you would ever create a Legend instance

manually. Most users would normally create a legend via the

:meth:`~matplotlib.axes.Axes.legend` function. For more details on legends

there is also a :doc:`legend guide </tutorials/intermediate/legend_guide>`.

The Legend class can be considered as a container of legend handles and

legend texts. Creation of corresponding legend handles from the plot elements

in the axes or figures (e.g., lines, patches, etc.) are specified by the

handler map, which defines the mapping between the plot elements and the

legend handlers to be used (the default legend handlers are defined in the

:mod:`~matplotlib.legend_handler` module). Note that not all kinds of

artist are supported by the legend yet by default but it is possible to

extend the legend handler's capabilities to support arbitrary objects. See

the :doc:`legend guide </tutorials/intermediate/legend_guide>` for more

information.

"""

import logging

import numpy as np

from matplotlib import cbook

from matplotlib import rcParams

from matplotlib import cbook, docstring

from matplotlib.artist import Artist, allow_rasterization

from matplotlib.cbook import silent_list, is_hashable, warn_deprecated

from matplotlib.font_manager import FontProperties

from matplotlib.lines import Line2D

from matplotlib.patches import Patch, Rectangle, Shadow, FancyBboxPatch

from matplotlib.collections import (LineCollection, RegularPolyCollection,

CircleCollection, PathCollection,

PolyCollection)

from matplotlib.transforms import Bbox, BboxBase, TransformedBbox

from matplotlib.transforms import BboxTransformTo, BboxTransformFrom

from matplotlib.offsetbox import HPacker, VPacker, TextArea, DrawingArea

from matplotlib.offsetbox import DraggableOffsetBox

from matplotlib.container import ErrorbarContainer, BarContainer, StemContainer

from . import legend_handler

<div class="viewcode-block" id="DraggableLegend"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.DraggableLegend">[docs]</a>class DraggableLegend(DraggableOffsetBox):

def __init__(self, legend, use_blit=False, update="loc"):

"""

Wrapper around a `.Legend` to support mouse dragging.

Parameters

----------

legend : `.Legend`

The `.Legend` instance to wrap.

use_blit : bool, optional

Use blitting for faster image composition. For details see

:ref:`func-animation`.

update : {'loc', 'bbox'}, optional

If "loc", update the *loc* parameter of the legend upon finalizing.

If "bbox", update the *bbox_to_anchor* parameter.

"""

self.legend = legend

if update in ["loc", "bbox"]:

self._update = update

else:

raise ValueError("update parameter '%s' is not supported." %

update)

DraggableOffsetBox.__init__(self, legend, legend._legend_box,

use_blit=use_blit)

<div class="viewcode-block" id="DraggableLegend.artist_picker"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.DraggableLegend.artist_picker">[docs]</a> def artist_picker(self, legend, evt):

return self.legend.contains(evt)</div>

<div class="viewcode-block" id="DraggableLegend.finalize_offset"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.DraggableLegend.finalize_offset">[docs]</a> def finalize_offset(self):

loc_in_canvas = self.get_loc_in_canvas()

if self._update == "loc":

self._update_loc(loc_in_canvas)

elif self._update == "bbox":

self._update_bbox_to_anchor(loc_in_canvas)

else:

raise RuntimeError("update parameter '%s' is not supported." %

self.update)</div>

def _update_loc(self, loc_in_canvas):

bbox = self.legend.get_bbox_to_anchor()

# if bbox has zero width or height, the transformation is

# ill-defined. Fall back to the defaul bbox_to_anchor.

if bbox.width == 0 or bbox.height == 0:

self.legend.set_bbox_to_anchor(None)

_bbox_transform = BboxTransformFrom(bbox)

self.legend._loc = tuple(

_bbox_transform.transform_point(loc_in_canvas)

)

def _update_bbox_to_anchor(self, loc_in_canvas):

tr = self.legend.axes.transAxes

loc_in_bbox = tr.transform_point(loc_in_canvas)

_legend_kw_doc = '''

loc : str or pair of floats, default: :rc:`legend.loc` ('best' for axes, \

'upper right' for figures)

The location of the legend.

The strings

``'upper left', 'upper right', 'lower left', 'lower right'``

place the legend at the corresponding corner of the axes/figure.

The strings

``'upper center', 'lower center', 'center left', 'center right'``

place the legend at the center of the corresponding edge of the

axes/figure.

The string ``'center'`` places the legend at the center of the axes/figure.

The string ``'best'`` places the legend at the location, among the nine

locations defined so far, with the minimum overlap with other drawn

artists. This option can be quite slow for plots with large amounts of

data; your plotting speed may benefit from providing a specific location.

The location can also be a 2-tuple giving the coordinates of the lower-left

corner of the legend in axes coordinates (in which case *bbox_to_anchor*

will be ignored).

For back-compatibility, ``'center right'`` (but no other location) can also

be spelled ``'right'``, and each "string" locations can also be given as a

numeric value:

=============== =============

Location String Location Code

=============== =============

'best' 0

'upper right' 1

'upper left' 2

'lower left' 3

'lower right' 4

'right' 5

'center left' 6

'center right' 7

'lower center' 8

'upper center' 9

'center' 10

=============== =============

bbox_to_anchor : `.BboxBase`, 2-tuple, or 4-tuple of floats

Box that is used to position the legend in conjunction with *loc*.

Defaults to `axes.bbox` (if called as a method to `.Axes.legend`) or

`figure.bbox` (if `.Figure.legend`). This argument allows arbitrary

placement of the legend.

Bbox coordinates are interpreted in the coordinate system given by

`bbox_transform`, with the default transform

Axes or Figure coordinates, depending on which ``legend`` is called.

If a 4-tuple or `.BboxBase` is given, then it specifies the bbox

``(x, y, width, height)`` that the legend is placed in.

To put the legend in the best location in the bottom right

quadrant of the axes (or figure)::

loc='best', bbox_to_anchor=(0.5, 0., 0.5, 0.5)

A 2-tuple ``(x, y)`` places the corner of the legend specified by *loc* at

x, y. For example, to put the legend's upper right-hand corner in the

center of the axes (or figure) the following keywords can be used::

loc='upper right', bbox_to_anchor=(0.5, 0.5)

ncol : integer

The number of columns that the legend has. Default is 1.

prop : None or :class:`matplotlib.font_manager.FontProperties` or dict

The font properties of the legend. If None (default), the current

:data:`matplotlib.rcParams` will be used.

fontsize : int or float or {'xx-small', 'x-small', 'small', 'medium', \

'large', 'x-large', 'xx-large'}

Controls the font size of the legend. If the value is numeric the

size will be the absolute font size in points. String values are

relative to the current default font size. This argument is only

used if `prop` is not specified.

numpoints : None or int

The number of marker points in the legend when creating a legend

entry for a `.Line2D` (line).

Default is ``None``, which will take the value from

:rc:`legend.numpoints`.

scatterpoints : None or int

The number of marker points in the legend when creating

a legend entry for a `.PathCollection` (scatter plot).

Default is ``None``, which will take the value from

:rc:`legend.scatterpoints`.

scatteryoffsets : iterable of floats

The vertical offset (relative to the font size) for the markers

created for a scatter plot legend entry. 0.0 is at the base the

legend text, and 1.0 is at the top. To draw all markers at the

same height, set to ``[0.5]``. Default is ``[0.375, 0.5, 0.3125]``.

markerscale : None or int or float

The relative size of legend markers compared with the originally

drawn ones.

Default is ``None``, which will take the value from

:rc:`legend.markerscale`.

markerfirst : bool

If *True*, legend marker is placed to the left of the legend label.

If *False*, legend marker is placed to the right of the legend

label.

Default is *True*.

frameon : None or bool

Control whether the legend should be drawn on a patch

(frame).

Default is ``None``, which will take the value from

:rc:`legend.frameon`.

fancybox : None or bool

Control whether round edges should be enabled around the

:class:`~matplotlib.patches.FancyBboxPatch` which makes up the

legend's background.

Default is ``None``, which will take the value from

:rc:`legend.fancybox`.

shadow : None or bool

Control whether to draw a shadow behind the legend.

Default is ``None``, which will take the value from

:rc:`legend.shadow`.

framealpha : None or float

Control the alpha transparency of the legend's background.

Default is ``None``, which will take the value from

:rc:`legend.framealpha`. If shadow is activated and

*framealpha* is ``None``, the default value is ignored.

facecolor : None or "inherit" or a color spec

Control the legend's background color.

Default is ``None``, which will take the value from

:rc:`legend.facecolor`. If ``"inherit"``, it will take

:rc:`axes.facecolor`.

edgecolor : None or "inherit" or a color spec

Control the legend's background patch edge color.

Default is ``None``, which will take the value from

:rc:`legend.edgecolor` If ``"inherit"``, it will take

:rc:`axes.edgecolor`.

mode : {"expand", None}

If `mode` is set to ``"expand"`` the legend will be horizontally

expanded to fill the axes area (or `bbox_to_anchor` if defines

the legend's size).

bbox_transform : None or :class:`matplotlib.transforms.Transform`

The transform for the bounding box (`bbox_to_anchor`). For a value

of ``None`` (default) the Axes'

:data:`~matplotlib.axes.Axes.transAxes` transform will be used.

title : str or None

The legend's title. Default is no title (``None``).

title_fontsize: str or None

The fontsize of the legend's title. Default is the default fontsize.

borderpad : float or None

The fractional whitespace inside the legend border.

Measured in font-size units.

Default is ``None``, which will take the value from

:rc:`legend.borderpad`.

labelspacing : float or None

The vertical space between the legend entries.

Measured in font-size units.

Default is ``None``, which will take the value from

:rc:`legend.labelspacing`.

handlelength : float or None

The length of the legend handles.

Measured in font-size units.

Default is ``None``, which will take the value from

:rc:`legend.handlelength`.

handletextpad : float or None

The pad between the legend handle and text.

Measured in font-size units.

Default is ``None``, which will take the value from

:rc:`legend.handletextpad`.

borderaxespad : float or None

The pad between the axes and legend border.

Measured in font-size units.

Default is ``None``, which will take the value from

:rc:`legend.borderaxespad`.

columnspacing : float or None

The spacing between columns.

Measured in font-size units.

Default is ``None``, which will take the value from

:rc:`legend.columnspacing`.

handler_map : dict or None

The custom dictionary mapping instances or types to a legend

handler. This `handler_map` updates the default handler map

found at :func:`matplotlib.legend.Legend.get_legend_handler_map`.

'''

docstring.interpd.update(_legend_kw_doc=_legend_kw_doc)

<div class="viewcode-block" id="Legend"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.Legend">[docs]</a>class Legend(Artist):

"""

Place a legend on the axes at location loc.

"""

codes = {'best': 0, # only implemented for axes legends

'upper right': 1,

'upper left': 2,

'lower left': 3,

'lower right': 4,

'right': 5,

'center left': 6,

'center right': 7,

'lower center': 8,

'upper center': 9,

'center': 10,

}

zorder = 5

def __str__(self):

return "Legend"

@docstring.dedent_interpd

def __init__(self, parent, handles, labels,

loc=None,

numpoints=None, # the number of points in the legend line

markerscale=None, # the relative size of legend markers

# vs. original

markerfirst=True, # controls ordering (left-to-right) of

# legend marker and label

scatterpoints=None, # number of scatter points

scatteryoffsets=None,

prop=None, # properties for the legend texts

fontsize=None, # keyword to set font size directly

# spacing & pad defined as a fraction of the font-size

borderpad=None, # the whitespace inside the legend border

labelspacing=None, # the vertical space between the legend

# entries

handlelength=None, # the length of the legend handles

handleheight=None, # the height of the legend handles

handletextpad=None, # the pad between the legend handle

# and text

borderaxespad=None, # the pad between the axes and legend

# border

columnspacing=None, # spacing between columns

ncol=1, # number of columns

mode=None, # mode for horizontal distribution of columns.

# None, "expand"

fancybox=None, # True use a fancy box, false use a rounded

# box, none use rc

shadow=None,

title=None, # set a title for the legend

title_fontsize=None, # set to ax.fontsize if None

framealpha=None, # set frame alpha

edgecolor=None, # frame patch edgecolor

facecolor=None, # frame patch facecolor

bbox_to_anchor=None, # bbox that the legend will be anchored.

bbox_transform=None, # transform for the bbox

frameon=None, # draw frame

handler_map=None,

):

"""

Parameters

----------

parent : `~matplotlib.axes.Axes` or `.Figure`

The artist that contains the legend.

handles : sequence of `.Artist`

A list of Artists (lines, patches) to be added to the legend.

labels : sequence of strings

A list of labels to show next to the artists. The length of handles

and labels should be the same. If they are not, they are truncated

to the smaller of both lengths.

Other Parameters

----------------

%(_legend_kw_doc)s

Notes

-----

Users can specify any arbitrary location for the legend using the

*bbox_to_anchor* keyword argument. bbox_to_anchor can be an instance

of BboxBase(or its derivatives) or a tuple of 2 or 4 floats.

See :meth:`set_bbox_to_anchor` for more detail.

The legend location can be specified by setting *loc* with a tuple of

2 floats, which is interpreted as the lower-left corner of the legend

in the normalized axes coordinate.

"""

# local import only to avoid circularity

from matplotlib.axes import Axes

from matplotlib.figure import Figure

Artist.__init__(self)

if prop is None:

if fontsize is not None:

self.prop = FontProperties(size=fontsize)

else:

elif isinstance(prop, dict):

self.prop = FontProperties(**prop)

if "size" not in prop:

self.prop.set_size(rcParams["legend.fontsize"])

else:

self.prop = prop

self._fontsize = self.prop.get_size_in_points()

self.texts = []

self.legendHandles = []

self._legend_title_box = None

#: A dictionary with the extra handler mappings for this Legend

#: instance.

self._custom_handler_map = handler_map

locals_view = locals()

for name in ["numpoints", "markerscale", "shadow", "columnspacing",

"scatterpoints", "handleheight", 'borderpad',

'labelspacing', 'handlelength', 'handletextpad',

'borderaxespad']:

if locals_view[name] is None:

value = rcParams["legend." + name]

else:

value = locals_view[name]

setattr(self, name, value)

del locals_view

# trim handles and labels if illegal label...

_lab, _hand = [], []

for label, handle in zip(labels, handles):

if isinstance(label, str) and label.startswith('_'):

cbook._warn_external('The handle {!r} has a label of {!r} '

'which cannot be automatically added to'

' the legend.'.format(handle, label))

else:

_lab.append(label)

_hand.append(handle)

labels, handles = _lab, _hand

handles = list(handles)

if len(handles) < 2:

ncol = 1

self._ncol = ncol

if self.numpoints <= 0:

raise ValueError("numpoints must be > 0; it was %d" % numpoints)

# introduce y-offset for handles of the scatter plot

if scatteryoffsets is None:

self._scatteryoffsets = np.array([3. / 8., 4. / 8., 2.5 / 8.])

else:

reps = self.scatterpoints // len(self._scatteryoffsets) + 1

reps)[:self.scatterpoints]

# _legend_box is an OffsetBox instance that contains all

# legend items and will be initialized from _init_legend_box()

# method.

self._legend_box = None

if isinstance(parent, Axes):

self.isaxes = True

self.axes = parent

self.set_figure(parent.figure)

elif isinstance(parent, Figure):

self.isaxes = False

self.set_figure(parent)

else:

raise TypeError("Legend needs either Axes or Figure as parent")

self.parent = parent

self._loc_used_default = loc is None

if loc is None:

loc = rcParams["legend.loc"]

if not self.isaxes and loc in [0, 'best']:

loc = 'upper right'

if isinstance(loc, str):

if loc not in self.codes:

if self.isaxes:

cbook.warn_deprecated(

"3.1", message="Unrecognized location {!r}. Falling "

"back on 'best'; valid locations are\n\t{}\n"

"This will raise an exception %(removal)s."

.format(loc, '\n\t'.join(self.codes)))

loc = 0

else:

cbook.warn_deprecated(

"back on 'upper right'; valid locations are\n\t{}\n'"

"This will raise an exception %(removal)s."

loc = 1

else:

loc = self.codes[loc]

if not self.isaxes and loc == 0:

cbook.warn_deprecated(

"3.1", message="Automatic legend placement (loc='best') not "

"implemented for figure legend. Falling back on 'upper "

"right'. This will raise an exception %(removal)s.")

loc = 1

self._mode = mode

self.set_bbox_to_anchor(bbox_to_anchor, bbox_transform)

# We use FancyBboxPatch to draw a legend frame. The location

# and size of the box will be updated during the drawing time.

if facecolor is None:

facecolor = rcParams["legend.facecolor"]

if facecolor == 'inherit':

facecolor = rcParams["axes.facecolor"]

if edgecolor is None:

edgecolor = rcParams["legend.edgecolor"]

if edgecolor == 'inherit':

edgecolor = rcParams["axes.edgecolor"]

self.legendPatch = FancyBboxPatch(

xy=(0.0, 0.0), width=1., height=1.,

facecolor=facecolor,

edgecolor=edgecolor,

mutation_scale=self._fontsize,

snap=True

)

# The width and height of the legendPatch will be set (in the

# draw()) to the length that includes the padding. Thus we set

# pad=0 here.

if fancybox is None:

fancybox = rcParams["legend.fancybox"]

if fancybox:

self.legendPatch.set_boxstyle("round", pad=0,

rounding_size=0.2)

else:

self.legendPatch.set_boxstyle("square", pad=0)

self._set_artist_props(self.legendPatch)

self._drawFrame = frameon

if frameon is None:

self._drawFrame = rcParams["legend.frameon"]

# init with null renderer

self._init_legend_box(handles, labels, markerfirst)

# If shadow is activated use framealpha if not

# explicitly passed. See Issue 8943

if framealpha is None:

if shadow:

self.get_frame().set_alpha(1)

else:

tmp = self._loc_used_default

self._set_loc(loc)

self._loc_used_default = tmp # ignore changes done by _set_loc

# figure out title fontsize:

if title_fontsize is None:

title_fontsize = rcParams['legend.title_fontsize']

tprop = FontProperties(size=title_fontsize)

self.set_title(title, prop=tprop)

self._draggable = None

def _set_artist_props(self, a):

"""

Set the boilerplate props for artists added to axes.

"""

a.set_figure(self.figure)

if self.isaxes:

# a.set_axes(self.axes)

a.axes = self.axes

a.set_transform(self.get_transform())

def _set_loc(self, loc):

# find_offset function will be provided to _legend_box and

# _legend_box will draw itself at the location of the return

# value of the find_offset.

self._loc_used_default = False

self._loc_real = loc

self.stale = True

self._legend_box.set_offset(self._findoffset)

def _get_loc(self):

return self._loc_real

_loc = property(_get_loc, _set_loc)

def _findoffset(self, width, height, xdescent, ydescent, renderer):

"Helper function to locate the legend."

if self._loc == 0: # "best".

x, y = self._find_best_position(width, height, renderer)

elif self._loc in Legend.codes.values(): # Fixed location.

bbox = Bbox.from_bounds(0, 0, width, height)

x, y = self._get_anchored_bbox(self._loc, bbox,

self.get_bbox_to_anchor(),

renderer)

else: # Axes or figure coordinates.

fx, fy = self._loc

bbox = self.get_bbox_to_anchor()

x, y = bbox.x0 + bbox.width * fx, bbox.y0 + bbox.height * fy

return x + xdescent, y + ydescent

<div class="viewcode-block" id="Legend.draw"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.Legend.draw">[docs]</a> @allow_rasterization

def draw(self, renderer):

"Draw everything that belongs to the legend."

if not self.get_visible():

return

renderer.open_group('legend')

fontsize = renderer.points_to_pixels(self._fontsize)

# if mode == fill, set the width of the legend_box to the

# width of the parent (minus pads)

if self._mode in ["expand"]:

pad = 2 * (self.borderaxespad + self.borderpad) * fontsize

self._legend_box.set_width(self.get_bbox_to_anchor().width - pad)

# update the location and size of the legend. This needs to

# be done in any case to clip the figure right.

bbox = self._legend_box.get_window_extent(renderer)

self.legendPatch.set_bounds(bbox.x0, bbox.y0,

bbox.width, bbox.height)

self.legendPatch.set_mutation_scale(fontsize)

if self._drawFrame:

if self.shadow:

shadow = Shadow(self.legendPatch, 2, -2)

shadow.draw(renderer)

self.legendPatch.draw(renderer)

self._legend_box.draw(renderer)

renderer.close_group('legend')

self.stale = False</div>

def _approx_text_height(self, renderer=None):

"""

Return the approximate height of the text. This is used to place

the legend handle.

"""

if renderer is None:

return self._fontsize

else:

return renderer.points_to_pixels(self._fontsize)

# _default_handler_map defines the default mapping between plot

# elements and the legend handlers.

_default_handler_map = {

StemContainer: legend_handler.HandlerStem(),

ErrorbarContainer: legend_handler.HandlerErrorbar(),

Line2D: legend_handler.HandlerLine2D(),

Patch: legend_handler.HandlerPatch(),

LineCollection: legend_handler.HandlerLineCollection(),

RegularPolyCollection: legend_handler.HandlerRegularPolyCollection(),

CircleCollection: legend_handler.HandlerCircleCollection(),

BarContainer: legend_handler.HandlerPatch(

update_func=legend_handler.update_from_first_child),

tuple: legend_handler.HandlerTuple(),

PathCollection: legend_handler.HandlerPathCollection(),

PolyCollection: legend_handler.HandlerPolyCollection()

}

# (get|set|update)_default_handler_maps are public interfaces to

# modify the default handler map.

<div class="viewcode-block" id="Legend.get_default_handler_map"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.Legend.get_default_handler_map">[docs]</a> @classmethod

def get_default_handler_map(cls):

"""

A class method that returns the default handler map.

"""

return cls._default_handler_map</div>

<div class="viewcode-block" id="Legend.set_default_handler_map"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.Legend.set_default_handler_map">[docs]</a> @classmethod

def set_default_handler_map(cls, handler_map):

"""

A class method to set the default handler map.

"""

cls._default_handler_map = handler_map</div>

<div class="viewcode-block" id="Legend.update_default_handler_map"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.Legend.update_default_handler_map">[docs]</a> @classmethod

def update_default_handler_map(cls, handler_map):

"""

A class method to update the default handler map.

"""

cls._default_handler_map.update(handler_map)</div>

<div class="viewcode-block" id="Legend.get_legend_handler_map"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.Legend.get_legend_handler_map">[docs]</a> def get_legend_handler_map(self):

"""

Return the handler map.

"""

default_handler_map = self.get_default_handler_map()

if self._custom_handler_map:

hm = default_handler_map.copy()

hm.update(self._custom_handler_map)

return hm

else:

return default_handler_map</div>

<div class="viewcode-block" id="Legend.get_legend_handler"><a class="viewcode-back" href="../../api/legend_api.html#matplotlib.legend.Legend.get_legend_handler">[docs]</a> @staticmethod

def get_legend_handler(legend_handler_map, orig_handle):

"""

Return a legend handler from *legend_handler_map* that

corresponds to *orig_handler*.

*legend_handler_map* should be a dictionary object (that is

returned by the get_legend_handler_map method).

It first checks if the *orig_handle* itself is a key in the

*legend_handler_map* and return the associated value.

Otherwise, it checks for each of the classes in its

method-resolution-order. If no matching key is found, it

returns ``None``.

"""

try:

return legend_handler_map[orig_handle]

except (TypeError, KeyError): # TypeError if unhashable.

pass

for handle_type in type(orig_handle).mro():

try:

return legend_handler_map[handle_type]

except KeyError:

pass

return None</div>

def _init_legend_box(self, handles, labels, markerfirst=True):

"""

Initialize the legend_box. The legend_box is an instance of

the OffsetBox, which is packed with legend handles and

texts. Once packed, their location is calculated during the

drawing time.

"""

fontsize = self._fontsize

# legend_box is a HPacker, horizontally packed with

# columns. Each column is a VPacker, vertically packed with

# legend items. Each legend item is HPacker packed with

# legend handleBox and labelBox. handleBox is an instance of

# offsetbox.DrawingArea which contains legend handle. labelBox

# is an instance of offsetbox.TextArea which contains legend

# text.

text_list = [] # the list of text instances

handle_list = [] # the list of text instances

handles_and_labels = []

label_prop = dict(verticalalignment='baseline',

horizontalalignment='left',

fontproperties=self.prop,

)

# The approximate height and descent of text. These values are

# only used for plotting the legend handle.

descent = 0.35 * self._approx_text_height() * (self.handleheight - 0.7)

# 0.35 and 0.7 are just heuristic numbers and may need to be improved.

height = self._approx_text_height() * self.handleheight - descent

# each handle needs to be drawn inside a box of (x, y, w, h) =

# (0, -descent, width, height). And their coordinates should

# be given in the display coordinates.

# The transformation of each handle will be automatically set

# to self.get_transform(). If the artist does not use its

# default transform (e.g., Collections), you need to

# manually set their transform to the self.get_transform().

legend_handler_map = self.get_legend_handler_map()

for orig_handle, lab in zip(handles, labels):

handler = self.get_legend_handler(legend_handler_map, orig_handle)

if handler is None:

cbook._warn_external(

"Legend does not support {!r} instances.\nA proxy artist "

"may be used instead.\nSee: "

"http://matplotlib.org/users/legend_guide.html"

"#creating-artists-specifically-for-adding-to-the-legend-"

"aka-proxy-artists".format(orig_handle))

# We don't have a handle for this artist, so we just defer

# to None.

handle_list.append(None)

else:

textbox = TextArea(lab, textprops=label_prop,

multilinebaseline=True,

minimumdescent=True)

handlebox = DrawingArea(width=self.handlelength * fontsize,

height=height,

xdescent=0., ydescent=descent)

text_list.append(textbox._text)

# Create the artist for the legend which represents the

# original artist/handle.

handle_list.append(handler.legend_artist(self, orig_handle,

fontsize, handlebox))

handles_and_labels.append((handlebox, textbox))

if handles_and_labels:

# We calculate number of rows in each column. The first

# (num_largecol) columns will have (nrows+1) rows, and remaining

# (num_smallcol) columns will have (nrows) rows.

ncol = min(self._ncol, len(handles_and_labels))

nrows, num_largecol = divmod(len(handles_and_labels), ncol)

num_smallcol = ncol - num_largecol

# starting index of each column and number of rows in it.

rows_per_col = [nrows + 1] * num_largecol + [nrows] * num_smallcol

start_idxs = np.concatenate([[0], np.cumsum(rows_per_col)[:-1]])

cols = zip(start_idxs, rows_per_col)

else:

cols = []

columnbox = []

for i0, di in cols:

# pack handleBox and labelBox into itemBox

itemBoxes = [HPacker(pad=0,

sep=self.handletextpad * fontsize,

children=[h, t] if markerfirst else [t, h],

align="baseline")

for h, t in handles_and_labels[i0:i0 + di]]

# minimumdescent=False for the text of the last row of the column

if markerfirst:

itemBoxes[-1].get_children()[1].set_minimumdescent(False)

else:

itemBoxes[-1].get_children()[0].set_minimumdescent(False)

# pack columnBox

alignment = "baseline" if markerfirst else "right"

columnbox.append(VPacker(pad=0,

sep=self.labelspacing * fontsize,

align=alignment,

children=itemBoxes))

mode = "expand" if self._mode == "expand" else "fixed"

sep = self.columnspacing * fontsize

self._legend_handle_box = HPacker(pad=0,

sep=sep, align="baseline",

mode=mode,

children=columnbox)

self._legend_title_box = TextArea("")

self._legend_box = VPacker(pad=self.borderpad * fontsize,

align="center",

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