matplotlib.pyplot.legend¶

matplotlib.pyplot.legend(*args, **kwargs)¶

Places a legend on the axes.

Call signatures:

legend()
legend(labels)
legend(handles, labels)

The call signatures correspond to three different ways how to use this method.

1. Automatic detection of elements to be shown in the legend

The elements to be added to the legend are automatically determined, when you do not pass in any extra arguments.

In this case, the labels are taken from the artist. You can specify them either at artist creation or by calling the set_label() method on the artist:

line, = ax.plot([1, 2, 3], label='Inline label')
ax.legend()

or:

line.set_label('Label via method')
line, = ax.plot([1, 2, 3])
ax.legend()

Specific lines can be excluded from the automatic legend element selection by defining a label starting with an underscore. This is default for all artists, so calling Axes.legend without any arguments and without setting the labels manually will result in no legend being drawn.

2. Labeling existing plot elements

To make a legend for lines which already exist on the axes (via plot for instance), simply call this function with an iterable of strings, one for each legend item. For example:

ax.plot([1, 2, 3])
ax.legend(['A simple line'])

Note: This way of using is discouraged, because the relation between plot elements and labels is only implicit by their order and can easily be mixed up.

3. Explicitly defining the elements in the legend

For full control of which artists have a legend entry, it is possible to pass an iterable of legend artists followed by an iterable of legend labels respectively:

legend((line1, line2, line3), ('label1', 'label2', 'label3'))

Parameters:

handles : sequence of Artist, optional

A list of Artists (lines, patches) to be added to the legend. Use this together with labels, if you need full control on what is shown in the legend and the automatic mechanism described above is not sufficient.

The length of handles and labels should be the same in this case. If they are not, they are truncated to the smaller length.

labels : sequence of strings, optional

A list of labels to show next to the artists. Use this together with handles, if you need full control on what is shown in the legend and the automatic mechanism described above is not sufficient.

Returns:

matplotlib.legend.Legend instance

Other Parameters:

loc : int or string or pair of floats, default: ‘upper right’

The location of the legend. Possible codes are:

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

Alternatively can be a 2-tuple giving x, y of the lower-left corner of the legend in axes coordinates (in which case bbox_to_anchor will be ignored).

bbox_to_anchor : BboxBase or pair of floats

Specify any arbitrary location for the legend in bbox_transform coordinates (default Axes coordinates).

For example, to put the legend’s upper right hand corner in the center of the axes 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 matplotlib.font_manager.FontProperties or dict

The font properties of the legend. If None (default), the current 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 line/matplotlib.lines.Line2D. Default is None which will take the value from the legend.numpoints rcParam.

scatterpoints : None or int

The number of marker points in the legend when creating a legend entry for a scatter plot/ matplotlib.collections.PathCollection. Default is None which will take the value from the legend.scatterpoints rcParam.

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 [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 the legend.markerscale rcParam.

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 the legend.frameon rcParam.

fancybox : None or bool

Control whether round edges should be enabled around the FancyBboxPatch which makes up the legend’s background. Default is None which will take the value from the legend.fancybox rcParam.

shadow : None or bool

Control whether to draw a shadow behind the legend. Default is None which will take the value from the legend.shadow rcParam.

framealpha : None or float

Control the alpha transparency of the legend’s background. Default is None which will take the value from the legend.framealpha rcParam. If shadow is activated and framealpha is None the default value is being ignored.

facecolor : None or “inherit” or a color spec

Control the legend’s background color. Default is None which will take the value from the legend.facecolor rcParam. If "inherit", it will take the axes.facecolor rcParam.

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 the legend.edgecolor rcParam. If "inherit", it will take the axes.edgecolor rcParam.

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 matplotlib.transforms.Transform

The transform for the bounding box (bbox_to_anchor). For a value of None (default) the Axes’ transAxes transform will be used.

title : str or None

The legend’s title. Default is no title (None).

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 the legend.borderpad rcParam.

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 the legend.labelspacing rcParam.

handlelength : float or None

The length of the legend handles. Measured in font-size units. Default is None which will take the value from the legend.handlelength rcParam.

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 the legend.handletextpad rcParam.

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 the legend.borderaxespad rcParam.

columnspacing : float or None

The spacing between columns. Measured in font-size units. Default is None which will take the value from the legend.columnspacing rcParam.

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 matplotlib.legend.Legend.get_legend_handler_map().

Notes

Not all kinds of artist are supported by the legend command. See Legend guide for details.

Examples

(Source code, png, pdf)