legend do not work without handles

[kinyatoride]

Description

There seem to be issues with get_legend_handles_labels when no handles are passed to ax.legend.
It would be better if this works as sometimes making handles are cumbersome.

Steps to reproduce

import proplot as plot

fig, ax = plot.subplots()
ax.plot([0, 1, 2], label='a')
ax.plot([0, 1, 1], label='b')
ax.legend()

Expected behavior: [What you expected to happen]
legend shows up

Actual behavior: [What actually happened]

ValueError Traceback (most recent call last)
in
4 ax.plot([0, 1, 2], label='a')
5 ax.plot([0, 1, 1], label='b')
----> 6 ax.legend()

~/miniconda3/envs/basic2/lib/python3.7/site-packages/proplot/ui.py in _iterator(*args, **kwargs)
680 result = []
681 for func in objs:
--> 682 result.append(func(*args, **kwargs))
683 if len(self) == 1:
684 return result[0]

~/miniconda3/envs/basic2/lib/python3.7/site-packages/proplot/axes/base.py in legend(self, loc, width, space, *args, **kwargs)
1399
1400 # Draw legend
-> 1401 return legend_wrapper(self, *args, loc=loc, **kwargs)
1402
1403 def draw(self, renderer=None, *args, **kwargs):

~/miniconda3/envs/basic2/lib/python3.7/site-packages/proplot/axes/plot.py in legend_wrapper(self, handles, labels, ncol, ncols, center, order, loc, label, title, fontsize, fontweight, fontcolor, color, marker, lw, linewidth, dashes, linestyle, markersize, frameon, frame, **kwargs)
3137 if list_of_lists:
3138 if any(not np.iterable(_) for _ in handles):
-> 3139 raise ValueError(f'Invalid handles={handles!r}.')
3140 if not labels:
3141 labels = [None] * len(handles)

ValueError: Invalid handles=[None].

Equivalent steps in matplotlib

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.plot([0, 1, 2], label='a')
ax.plot([0, 1, 1], label='b')

ax.legend()

Proplot version

0.63

[lukelbd]

Thanks for the report, this is fixed now. Another issue that highlights the need for more robust testing

[GonzaloSaez]

Hi @lukelbd ,

Is it possible to call legend on an axis of a given plot of a subplots without the handles argument? Whenever I try this I get an error:

ax[1].legend(loc='b', ncols=4, center=True)

Error:

line 3362, in legend_wrapper interval = 1 / len(pairs) # split up axes ZeroDivisionError: division by zero

It would be nice if the legend could directly access the default handles without relying on their generation when plotting...

[lukelbd]

Hi @ssssoo -- thanks for the report!

This was an unfortunate bug that occured when using the "side" locations instead of an inner location like 'upper left'. I copied your comment into a dedicated thread (#189), it's now fixed in the master branch.

[kinyatoride]

Hi @lukelbd

This issue still appears when loc is passed.

ax.legend(loc='b')

Error:

No handles with labels found to put in legend.
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-58dceaf93eec> in <module>
      4 ax.plot([0, 1, 2], label='a')
      5 ax.plot([0, 1, 1], label='b')
----> 6 ax.legend(loc='b')

~/miniconda3/envs/basic/lib/python3.8/site-packages/proplot/ui.py in _iterator(*args, **kwargs)
    680                 result = []
    681                 for func in objs:
--> 682                     result.append(func(*args, **kwargs))
    683                 if len(self) == 1:
    684                     return result[0]

~/miniconda3/envs/basic/lib/python3.8/site-packages/proplot/axes/base.py in legend(self, loc, width, space, *args, **kwargs)
   1369         if loc in ('left', 'right', 'top', 'bottom'):
   1370             ax = self.panel_axes(loc, width=width, space=space, filled=True)
-> 1371             return ax.legend(*args, loc='fill', **kwargs)
   1372 
   1373         # Fill

~/miniconda3/envs/basic/lib/python3.8/site-packages/proplot/axes/base.py in legend(self, loc, width, space, *args, **kwargs)
   1399 
   1400         # Draw legend
-> 1401         return legend_wrapper(self, *args, loc=loc, **kwargs)
   1402 
   1403     def draw(self, renderer=None, *args, **kwargs):

~/miniconda3/envs/basic/lib/python3.8/site-packages/proplot/axes/plot.py in legend_wrapper(self, handles, labels, ncol, ncols, center, order, loc, label, title, fontsize, fontweight, fontcolor, color, marker, lw, linewidth, dashes, linestyle, markersize, frameon, frame, **kwargs)
   3329 
   3330         # Draw legend
-> 3331         leg = mlegend.Legend(self, *zip(*pairs), ncol=ncol, loc=loc, **kwargs)
   3332         legs = [leg]
   3333 

TypeError: __init__() missing 2 required positional arguments: 'handles' and 'labels'

[lukelbd]

@kinyatoride It should be fixed on master; do you have the "development" version? Can be installed with pip install git+https://github.com/lukelbd/proplot

[kinyatoride]

@lukelbd

This issue appears again in the development version (0.8.0.post5).

Error:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/tmp/ipykernel_92559/3733033338.py in <module>
      5 ax.plot([0, 1, 1], label='b')
      6 #ax.legend(loc='b')
----> 7 ax.legend()

~/miniconda3/envs/basicf5/lib/python3.9/site-packages/proplot/figure.py in _grid_command(self, *args, **kwargs)
   2004         objs = []
   2005         for ax in self:
-> 2006             obj = getattr(ax, name)(*args, **kwargs)
   2007             if obj is not None:
   2008                 objs.append(obj)

~/miniconda3/envs/basicf5/lib/python3.9/site-packages/proplot/axes/base.py in legend(self, handles, labels, loc, location, queue, **kwargs)
   2765             self._add_guide('legend', obj, loc, **kwargs)
   2766         else:
-> 2767             leg = self._draw_legend(handles, labels, loc=loc, **kwargs)
   2768             return leg
   2769 

~/miniconda3/envs/basicf5/lib/python3.9/site-packages/proplot/axes/base.py in _draw_legend(self, handles, labels, loc, width, pad, space, frame, frameon, ncol, ncols, alphabetize, center, order, label, title, fontsize, fontweight, fontcolor, titlefontsize, titlefontweight, titlefontcolor, **kwargs)
   2638             else:  # figure panel i.e. figure-wide legend
   2639                 axs = list(self.figure._iter_axes(hidden=False, children=True))
-> 2640         pairs = self._parse_handles_labels(
   2641             axs, handles, labels,
   2642             ncol=ncol, order=order, center=center, alphabetize=alphabetize,

~/miniconda3/envs/basicf5/lib/python3.9/site-packages/proplot/axes/base.py in _parse_handles_labels(self, axs, handles, labels, ncol, order, center, alphabetize)
   2339         axs = axs or ()
   2340         handles, labels = _to_list(handles), _to_list(labels)
-> 2341         list_of_lists = any(isinstance(h, (list, np.ndarray)) and len(h) > 1 for h in handles)  # noqa: E501
   2342         if list_of_lists and ncol is not None:
   2343             warnings._warn_proplot(

TypeError: 'NoneType' object is not iterable

[lukelbd]

Thanks, this was another quick fix (fdd53a6). The refactors in v0.8 had been hanging over my head for 2 years -- now that they're finally done the next step is obviously to add many many more automated tests (goal for the end of 2021).

import proplot as plot
fig, ax = plot.subplots()
ax.plot([0, 1, 2], label='a')
ax.plot([0, 1, 1], label='b')
ax.legend()

import proplot as plot
fig, ax = plot.subplots()
ax.plot([0, 1, 2])
ax.plot([0, 1, 1])
ax.legend(labels=['a', 'b'])