Remove optparse from example (#655)

* replace optparse with click

* remove click entirely

examples/demo/advanced/scalar_image_function_inspector.py

@@ -12,8 +12,6 @@
 
 
 # Standard library imports
-from optparse import OptionParser
-import sys
 import random
 
 # Major library imports
@@ -450,8 +448,10 @@ def _colormap_changed(self):
 
     def _num_levels_changed(self):
         if self.num_levels > 3:
-            self.polyplot.levels = self.num_levels
-            self.lineplot.levels = self.num_levels
+            if self.polyplot is not None:
+                self.polyplot.levels = self.num_levels
+            if self.lineplot is not None:
+                self.lineplot.levels = self.num_levels
 
 
 # HasTraits class that supplies the callable for the timer event.
@@ -634,56 +634,5 @@ def show_plot(**kwargs):
     modelview.configure_traits()
 
 
-def main(argv=None):
-
-    if argv is None:
-        argv = sys.argv
-
-    usage = "usage: %prog [options]"
-    parser = OptionParser(usage=usage, version="%prog 1.0")
-
-    parser.add_option(
-        "-c",
-        "--colormap",
-        action="store",
-        type="string",
-        dest="colormap",
-        default="viridis",
-        metavar="CMAP",
-        help="choose a default colormapper",
-    )
-
-    parser.add_option(
-        "-n",
-        "--nlevels",
-        action="store",
-        type="int",
-        dest="num_levels",
-        default=15,
-        help="number countour levels to plot [default: %default]",
-    )
-
-    parser.add_option(
-        "-f",
-        "--function",
-        action="store",
-        type="string",
-        dest="function",
-        default="tanh(x**2+y)*cos(y)*jn(0,x+y*2)",
-        help="function of x and y [default: %default]",
-    )
-
-    opts, args = parser.parse_args(argv[1:])
-
-    if len(args) > 0:
-        parser.error("Incorrect number of arguments")
-
-    show_plot(
-        colormap=opts.colormap,
-        num_levels=opts.num_levels,
-        function=opts.function,
-    )
-
-
 if __name__ == "__main__":
-    sys.exit(main())
+    show_plot()