content: from __future__ import (absolute_import, division, print_function,
                          unicode_literals)
  
  from matplotlib.externals import six
  
  import numpy as np
  from matplotlib.tri.triangulation import Triangulation
  
  
  def triplot(ax, *args, **kwargs):
      """
      Draw a unstructured triangular grid as lines and/or markers.
  
      The triangulation to plot can be specified in one of two ways;
      either::
  
        triplot(triangulation, ...)
  
      where triangulation is a :class:`matplotlib.tri.Triangulation`
      object, or
  
      ::
  
        triplot(x, y, ...)
        triplot(x, y, triangles, ...)
        triplot(x, y, triangles=triangles, ...)
        triplot(x, y, mask=mask, ...)
        triplot(x, y, triangles, mask=mask, ...)
  
      in which case a Triangulation object will be created.  See
      :class:`~matplotlib.tri.Triangulation` for a explanation of these
      possibilities.
  
      The remaining args and kwargs are the same as for
      :meth:`~matplotlib.axes.Axes.plot`.
  
      Return a list of 2 :class:`~matplotlib.lines.Line2D` containing
      respectively:
  
          - the lines plotted for triangles edges
          - the markers plotted for triangles nodes
  
      **Example:**
  
          .. plot:: mpl_examples/pylab_examples/triplot_demo.py
      """
      import matplotlib.axes
  
      tri, args, kwargs = Triangulation.get_from_args_and_kwargs(*args, **kwargs)
      x, y, edges = (tri.x, tri.y, tri.edges)
  
      # Decode plot format string, e.g., 'ro-'
      fmt = ""
      if len(args) > 0:
          fmt = args[0]
      linestyle, marker, color = matplotlib.axes._base._process_plot_format(fmt)
  
      # Insert plot format string into a copy of kwargs (kwargs values prevail).
      kw = kwargs.copy()
      for key, val in zip(('linestyle', 'marker', 'color'),
                          (linestyle, marker, color)):
          if val is not None:
              kw[key] = kwargs.get(key, val)
  
      # Draw lines without markers.
      # Note 1: If we drew markers here, most markers would be drawn more than
      #         once as they belong to several edges.
      # Note 2: We insert nan values in the flattened edges arrays rather than
      #         plotting directly (triang.x[edges].T, triang.y[edges].T)
      #         as it considerably speeds-up code execution.
      linestyle = kw['linestyle']
      kw_lines = kw.copy()
      kw_lines['marker'] = 'None'  # No marker to draw.
      kw_lines['zorder'] = kw.get('zorder', 1)  # Path default zorder is used.
      if (linestyle is not None) and (linestyle not in ['None', '', ' ']):
          tri_lines_x = np.insert(x[edges], 2, np.nan, axis=1)
          tri_lines_y = np.insert(y[edges], 2, np.nan, axis=1)
          tri_lines = ax.plot(tri_lines_x.ravel(), tri_lines_y.ravel(),
                              **kw_lines)
      else:
          tri_lines = ax.plot([], [], **kw_lines)
  
      # Draw markers separately.
      marker = kw['marker']
      kw_markers = kw.copy()
      kw_markers['linestyle'] = 'None'  # No line to draw.
      if (marker is not None) and (marker not in ['None', '', ' ']):
          tri_markers = ax.plot(x, y, **kw_markers)
      else:
          tri_markers = ax.plot([], [], **kw_markers)
  
      return tri_lines + tri_markers
  