title: My Python codes for making a bokeh plot are giving a blank plot
body: <p>I am using Jupyter Notebook to run my Python codes. The issue with my codes is that the output is giving a blank plot (not any error message from Python).</p>
  
  <p>My codes stand as follows:</p>
  
  <pre><code>from bokeh.layouts import row
  from bokeh.plotting import figure, show, output_file
  
  data = myBenchmarkData
  factors = ["Group"]
  x =  ["Rate"]
  
  dot = figure(title="Categorical Dot Plot", tools="", toolbar_location=None,
          y_range=factors, x_range=[0,200])
  
  dot.segment(0, factors, x, factors, line_width=2, line_color="green", )
  dot.circle(x, factors, size=15, fill_color="orange", line_color="green", line_width=3, )
  
   output_file("categorical.html", title="categorical.py example")
   show(row(dot, sizing_mode="scale_width"))
  </code></pre>
  
  <p>When I run these bunch of codes, it does execute correctly by creating a new html file but the page shows a blank plot with the word "Group" mentioned on the y-axis.
  My data comes from a csv file and it has been imported correctly. "Group" and "Rate" are series (column names) from my dataframe.</p>
  
  <p>I did a test and hardcoded the list for factors and x, and the plot worked fine. It seems my codes are not understanding that I want to retrieve the factors list from the "Group" column and the x list from the "Rate" column of my dataframe.</p>