drag_tool.py

from bokeh.models import Tool, Plot, Range1d, LinearAxis, Span
from bokeh.core.properties import Instance
from bokeh.io import output_file, show

DEFAULT_OVERLAY = lambda: Span(
    render_mode='css',
    level="overlay",
    location_units="screen",
)

class DragTool(Tool):
    __implementation__ = """
_ = require "underscore"

GestureTool = require "models/tools/gestures/gesture_tool"
Span = require "models/annotations/span"
p = require "core/properties"

class DragToolView extends GestureTool.View

  initialize: (options) ->
    super(options)
    @listenTo(@model, 'change:active', @_active_change)

  _active_change: () ->
    if not @mget('active')
      @mget('overlay').unset('location')

  _pan_start: (e) ->
    return null

  _pan: (e) ->
    frame = @plot_model.get('frame')
    canvas = @plot_view.canvas
    overlay = @mget('overlay')

    vx = canvas.sx_to_vx(e.bokeh.sx)
    vy = canvas.sy_to_vy(e.bokeh.sy)

    if not frame.contains(vx, vy)
      overlay.unset('location')
      return null

    if overlay.get('dimension') == 'width'
        overlay.set({location: vy})
    else
        overlay.set({location: vx})

  _pan_end: (e) ->
    return null

DEFAULT_OVERLAY = () -> new Span.Model({
  render_mode: "css"
  level: "overlay"
  location_units: "screen"
})

class DragTool extends GestureTool.Model
  default_view: DragToolView
  type: "DragTool"
  tool_name: "Drag Span"
  icon: "bk-tool-icon-lasso-select"
  event_type: "pan"
  default_order: 12

  @define {
      overlay:                [ p.Instance, DEFAULT_OVERLAY ]
    }

module.exports =
  Model: DragTool
  View: DragToolView

    """

    overlay = Instance(Span, default=DEFAULT_OVERLAY, help="""
    Span instance to to be dragged
    """)

output_file('out.html')

plot = Plot(plot_width=600, plot_height=600,
            x_range=Range1d(0,10), y_range=Range1d(0,10))
plot.add_tools(DragTool())
plot.add_layout(LinearAxis(), 'below')
plot.add_layout(LinearAxis(), 'left')

show(plot)

Hi. I'm trying to run this code. I'm getting an error. "RuntimeError: no such module: underscore"
Any solution? Thanks