Legend labels for ``plot``

Previously if a sequence was passed to the *label* parameter of `~.Axes.plot` when

plotting a single dataset, the sequence was automatically cast to string for the legend

label. Now, if the sequence has only one element, that element will be the legend

label. To keep the old behavior, cast the sequence to string before passing.

Legend labels for ``plot``

Previously if a sequence was passed to the *label* parameter of `~.Axes.plot` when

plotting a single dataset, the sequence was automatically cast to string for the legend

label. This behavior is now deprecated and in future will error if the sequence length

is not one (consistent with multi-dataset behavior, where the number of elements must

match the number of datasets). To keep the old behavior, cast the sequence to string

before passing.

label=kwargs.get('label')

n_datasets=max(ncx,ncy)

ifn_datasets>1andnotcbook.is_scalar_or_string(label):

iflen(label)!=n_datasets:

raiseValueError(f"label must be scalar or have the same "

f"{len(label)} for{n_datasets} datasets.")

ifcbook.is_scalar_or_string(label):

labels= [label]*n_datasets

eliflen(label)==n_datasets:

elifn_datasets==1:

msg= (f'Passing label as a length{len(label)} sequence when '

'cast the sequence to string before passing.')

_api.warn_deprecated('3.9',message=msg)

labels= [label]

else:

labels= [label]*n_datasets

raiseValueError(

f"data, but found{len(label)} for{n_datasets} datasets.")

result= (make_artist(axes,x[:,j%ncx],y[:,j%ncy],kw,

{**kwargs,'label':label})

x= [1,2,3]

y= [2,5,6]

fig,ax=plt.subplots()

ax.plot(x,y,label=label_array)

withpytest.warns(mpl.MatplotlibDeprecationWarning,

match='Passing label as a length 2 sequence'):

ax.plot(x,y,label=label_array)

leg=ax.legend()

assertlen(leg.get_texts())==1

assertleg.get_texts()[0].get_text()==str(label_array)

deftest_plot_single_input_list_label():

fig,ax=plt.subplots()

line,=ax.plot([[0], [1]],label=['A'])

assertline.get_label()=='A'

deftest_plot_multiple_label_incorrect_length_exception():