Correct me if I’m wrong, but it looks like you used the
figure_factory.create_gantt function to build the original figure, and then added a scatter trace afterward.
The issue you’re running into is that the bars in the Gantt chart aren’t traces like the scatter trace, they are shapes (See https://plot.ly/python/shapes/), so they don’t follow the same layering rules as traces. That’s why the scatter trace you appended to the end doesn’t end up on top.
Fortunately, shapes have their own
layer property (See https://plot.ly/python/reference/#layout-shapes-layer) that you can be set to
'above' (the default) or
'below' (what I think you want).
The figure factor function doesn’t have an option to change the layer, but you can do so after the figure is constructed like this
for bar in fig['layout']['shapes']:
bar['layer'] = 'below'
Also, in case it’s helpful for lining up your own scatter trace, you can also get the coordinates of each rectangle by looping over the shapes. e.g.
x0s = [bar['x0'] for bar in fig['layout']['shapes']]
x1s = [bar['x1'] for bar in fig['layout']['shapes']]
y0s = [bar['y0'] for bar in fig['layout']['shapes']]
y1s = [bar['y1'] for bar in fig['layout']['shapes']]
Hope that helps!