@@ -18,6 +18,7 @@

 import warnings

 from math import sqrt, pi

 import numpy as np

+from enum import Enum

 try:

     import matplotlib

@@ -34,11 +35,34 @@ try:

         warnings.warn("3D plotting not available.", RuntimeWarning)

         has3d = False

 except ImportError:

-    warnings.warn("matplotlib is not available, only iterator-providing "

-                  "functions will work.", RuntimeWarning)

+    warnings.warn("matplotlib is not available, if other backends are "

+                  "unavailable, only iterator-providing functions will work",

+                  RuntimeWarning)

     mpl_available = False

+try:

+    import plotly.offline as plotly

+    import plotly.graph_objs as plotly_graph_objs

+    plotly.init_notebook_mode(connected=True)

+    plotly_available = True

+except ImportError:

+    warnings.warn("plotly is not available, if other backends are unavailable,"

+                  " only iterator-providing functions will work",

+                  RuntimeWarning)

+    plotly_available = False

+

+

+class Backends(Enum):

+    matplotlib = 0

+    plotly = 1

+

+backend = Backends.matplotlib

+

+if not ((mpl_available) or (plotly_available)):

+    backend = None

+

+

 # Collections that allow for symbols and linewiths to be given in data space

 # (not for general use, only implement what's needed for plotter)

 def isarray(var):

@@ -30,7 +30,8 @@ from . import system, builder, _common

 from ._common import deprecate_args

-__all__ = ['plot', 'map', 'bands', 'spectrum', 'current', 'density',

+__all__ = ['set_backend',

+           'plot', 'map', 'bands', 'spectrum', 'current', 'density',

            'interpolate_current', 'interpolate_density',

            'streamplot', 'scalarplot',

            'sys_leads_sites', 'sys_leads_hoppings', 'sys_leads_pos',

@@ -41,6 +42,43 @@ __all__ = ['plot', 'map', 'bands', 'spectrum', 'current', 'density',

 _p = _common.lazy_import('_plotter')

+def set_backend(backend):

+    """Set the plotting backend to use.

+

+    Parameters

+    ----------

+    backend : str

+        Options are: 'matplotlib', 'plotly'.

+    """

+

+    if ((_p.mpl_available) or (_p.plotly_available)):

+        try:

+            _p.backend = _p.Backends[backend]

+        except KeyError:

+            list_available_backends = []

+            if (_p.mpl_available):

+                list_available_backends.append('matplotlib')

+            if (_p.plotly_available):

+                list_available_backends.append('plotly')

+            error_message = "Tried to set an unknown backend \'{}\'.".format(

+                                                                       backend)

+            error_message += " Supported backends are {}".format(

+                                                       list_available_backends)

+            raise RuntimeError(error_message)

+    else:

+        warnings.warn("Tried to set \'{}\' but is not "

+                      "available.".format(backend), RuntimeWarning)

+

+    if (_p.is_ipython_kernel):

+        if ((_p.backend == _p.Backends.plotly) and

+            (not _p.init_notebook_mode_set)):

+            _p.init_notebook_mode_set = True

+            _p.plotly_module.init_notebook_mode(connected=True)

+

+

+def get_backend():

+    return _p.backend

+

 def _sample_array(array, n_samples, rng=None):

     rng = _common.ensure_rng(rng)

     la = len(array)

@@ -106,13 +144,19 @@ def _maybe_output_fig(fig, file=None, show=True):

     if fig is None:

         return

-    if file is not None:

-        fig.canvas.print_figure(file, dpi=fig.dpi)

-    elif show:

-        # If there was no file provided, pyplot should already be available and

-        # we can import it safely without additional warnings.

-        from matplotlib import pyplot

-        pyplot.show()

+    if get_backend() == _p.Backends.matplotlib:

+        if file is not None:

+            fig.canvas.print_figure(file, dpi=fig.dpi)

+        elif show:

+            # If there was no file provided, pyplot should already be available

+            # and we can import it safely without additional warnings.

+            from matplotlib import pyplot

+            pyplot.show()

+    elif get_backend() == _p.Backends.plotly:

+        if file is not None:

+            _p.plotly.plot(fig, show_link=False, filename=file, auto_open=False)

+        if show:

+            _p.plotly.iplot(fig)

 def set_colors(color, collection, cmap, norm=None):

@@ -585,7 +585,8 @@ def main():

                             'tinyarray >= 1.2'],

           extras_require={

               # The oldest versions between: Debian stable, Ubuntu LTS

-              'plotting': 'matplotlib >= 2.1.1',

+              'plotting': ['matplotlib >= 2.1.1',

+                           'plotly >= 2.2.2'],

               'continuum': 'sympy >= 1.1.1',

               # qsymm is only packaged on PyPI

               'qsymm': 'qsymm >= 1.2.6',