Why do I get NonGuiException in jupyter notebook when trying to plot using matplotlib inline?

Question

I get an error when trying to plot inline in a jupyter notebook.

%matplotlib inline
N = 20
M = 10
df = pd.DataFrame(
    index=pd.date_range(dtt.date.today(), periods=N),
    data=np.random.randn(N, M),
    columns=['path_{}'.format(ii) for ii in range(M)]
)
df.plot()

I get the following NonGuiException error. Even though the image plots it seems to raise an exception. If as the index to the dataframe I use range(N) it works just fine which is strange.

Any ideas what is going on? --------------------------------------------------------------------------- NonGuiException Traceback (most recent call last) in () 6 columns=['path_{}'.format(ii) for ii in range(M)] 7 ) ----> 8 df.plot()

/usr/local/lib/python3.5/dist-packages/pandas/tools/plotting.py in
__call__(self, x, y, kind, ax, subplots, sharex, sharey, layout, figsize, use_index, title, grid, legend, style, logx, logy, loglog, xticks, yticks, xlim, ylim, rot, fontsize, colormap, table, yerr, xerr, secondary_y, sort_columns, **kwds)    3771                       fontsize=fontsize, colormap=colormap, table=table,    3772             yerr=yerr, xerr=xerr, secondary_y=secondary_y,
-> 3773                           sort_columns=sort_columns, **kwds)    3774     __call__.__doc__ = plot_frame.__doc__    3775 

/usr/local/lib/python3.5/dist-packages/pandas/tools/plotting.py in plot_frame(data, x, y, kind, ax, subplots, sharex, sharey, layout, figsize, use_index, title, grid, legend, style, logx, logy, loglog, xticks, yticks, xlim, ylim, rot, fontsize, colormap, table, yerr, xerr, secondary_y, sort_columns, **kwds)    2640                  yerr=yerr, xerr=xerr,    2641                  secondary_y=secondary_y, sort_columns=sort_columns,
-> 2642                  **kwds)    2643     2644 

/usr/local/lib/python3.5/dist-packages/pandas/tools/plotting.py in
_plot(data, x, y, subplots, ax, kind, **kwds)    2467         plot_obj = klass(data, subplots=subplots, ax=ax, kind=kind, **kwds)    2468 
-> 2469     plot_obj.generate()    2470     plot_obj.draw()    2471     return plot_obj.result

/usr/local/lib/python3.5/dist-packages/pandas/tools/plotting.py in generate(self)    1041         self._compute_plot_data()    1042       self._setup_subplots()
-> 1043         self._make_plot()    1044         self._add_table()    1045         self._make_legend()

/usr/local/lib/python3.5/dist-packages/pandas/tools/plotting.py in
_make_plot(self)    1724                              stacking_id=stacking_id,    1725                              is_errorbar=is_errorbar,
-> 1726                              **kwds)    1727             self._add_legend_handle(newlines[0], label, index=i)    1728 

/usr/local/lib/python3.5/dist-packages/pandas/tools/plotting.py in
_ts_plot(cls, ax, x, data, style, **kwds)    1764         lines = cls._plot(ax, data.index, data.values, style=style, **kwds)    1765   
# set date formatter, locators and rescale limits
-> 1766         format_dateaxis(ax, ax.freq)    1767         return lines    1768 

/usr/local/lib/python3.5/dist-packages/pandas/tseries/plotting.py in format_dateaxis(subplot, freq)
    292         "t = {0}  y = {1:8f}".format(Period(ordinal=int(t), freq=freq), y))
    293 
--> 294     pylab.draw_if_interactive()

/usr/local/lib/python3.5/dist-packages/IPython/utils/decorators.py in wrapper(*args, **kw)
     41     def wrapper(*args,**kw):
     42         wrapper.called = False
---> 43         out = func(*args,**kw)
     44         wrapper.called = True
     45         return out

/usr/lib/python3/dist-packages/matplotlib/backends/backend_tkagg.py in draw_if_interactive()
     68         figManager =  Gcf.get_active()
     69         if figManager is not None:
---> 70             figManager.show()
     71 
     72 class Show(ShowBase):

/usr/lib/python3/dist-packages/matplotlib/backend_bases.py in show(self)    2618         optional warning.    2619         """
-> 2620         raise NonGuiException()    2621     2622     def destroy(self):

NonGuiException:

Answer 1

The command %matplotlib inline sets the backend . Check you haven't set a conflicting backend somewhere else .

I found that I had set my MPLBACKEND environment variable to TkAgg . As soon as I deleted it from my pipenv .env file and restarted my shell and Jupyter notebook server, inline ploting worked again.