Python Pandas Bokeh Indexerror: list index out of range - why?

I'm having trouble with the code below:

from bokeh.plotting import figure, output_file, show, save
from bokeh.models import ColumnDataSource
from bokeh.models import Range1d, LinearAxis
import pandas as pd
from pandas import HDFStore
from bokeh.palettes import Spectral9

store = pd.HDFStore('<hdf store location>')
df = pd.DataFrame(store['d1'])
df = df.rename_axis('Time')
df.fillna(0)

#the number of colums is the number of lines that we will make
numlines = len(df.columns)

#import colour pallet
mypalette = Spectral9[0:numlines]

# remove unwanted columns
col_list = ['Col1', 'Col2', 'Col3']
df = df[col_list]

# make the figure, 
p = figure(x_axis_type="datetime", title="<title>", width = 800, height = 450)
p.xaxis.axis_label = 'Date'
p.yaxis.axis_label = '<y axis label>'

p.line(df.index, df['Col1'], legend = 'Col1', color = mypalette[0] )
p.line(df.index, df['Col2'], legend = 'Col2', color = mypalette[1] )

# add extra y axis
p.extra_y_ranges = {'Col3': Range1d(start=0, end=1)}
p.circle(df.index, df['Col3'], legend = 'Col3', color = mypalette[8], 
     y_range_name='Col3' )
p.add_layout(LinearAxis(y_range_name='Col3'), 'right')


# creates an output file 
output_file('<output file location>')

#save the plot
save(p)

This is what my dataframe looks like:

  Time              Col1     Col2     Col3     Col4
29/11/2016 00:00    4        41       41        55
29/11/2016 01:00    55       15       61        81
29/11/2016 02:00    51       75       2         4
29/11/2016 03:00    21       21       51        9
etc.

When I try to run the code above, I get the following error:

IndexError                                Traceback (most recent call last)
<ipython-input-20-9d2c8911130d> in <module>()
38 
39 # add extra y axis
---> 40 p.circle(df.index, df['Col3'], legend = 'Col3', color = mypalette[8],  y_range_name='Col3')
 41 p.add_layout(LinearAxis(y_range_name='Col3'), 'right')
 42 

IndexError: list index out of range

I can't seem to work out what I am doing wrong. Can anyone help?

Solution

The following lines appear towards the top of your code.

#the number of colums is the number of lines that we will make
numlines = len(df.columns)

#import colour pallet
mypalette = Spectral9[0:numlines]

In the first line, you set numlines equal to the number of columns you have. You only have 4 columns in your dataframe. In your second line, you set mypalette equal to the first N elements of Spectral9, where n is the number of lines you have. As such, your palette is limited to the first 4 elements of Spectral9.

Later in your code, you try to grab the 9th element of mypalette (which would be [8] with zero-indexing in python).

p.circle(df.index, df['Col3'], legend = 'Col3', color = mypalette[8], 
     y_range_name='Col3' )

You limited mypalette to have only 4 elements, so mypalette[8] is out of range. If you want to use that specific color, you can consider using color = Spectral9[8] instead of color = mypalette[8].