Compute difference between spectral indices

import glob, os
import pandas as pd
import rasterio
import rasterio.plot
from pathlib import Path

print('All libraries successfully imported!')

All libraries successfully imported!

index_name = 'NDVI'

Set directory

computer_path = '/export/miro/ndeffense/LBRAT2104/'
grp_letter    = 'X'

# Directory for all work files
work_path = f'{computer_path}GROUP_{grp_letter}/WORK/'

index_path = f'{work_path}{index_name}/'

index_calc_path = f'{work_path}{index_name}_CALC/'

Path(index_calc_path).mkdir(parents=True, exist_ok=True)

# Choose the two dates you want to subtract
date_1 = '20170707'
date_2 = '20200731'

# Get the spectral indices associated with the dates you have chosen
index_file_1 = glob.glob(f'{index_path}*{date_1}*.tif')[0]
index_file_2 = glob.glob(f'{index_path}*{date_2}*.tif')[0]

# Name the output index file
index_file_diff = f'{index_calc_path}{index_name}_{date_2}_MINUS_{date_1}.tif'

if not os.path.isfile(index_file_diff):

    # Open the spectral index at date 1
    src = rasterio.open(index_file_1, 'r')
    profile = src.profile
    date_1_arr = src.read(1)
    src.close()

    # Open the spectral index at date 2
    src = rasterio.open(index_file_2, 'r')
    date_2_arr = src.read(1)
    src.close()

    # Compute the difference between date 2 and date 1
    diff_index = date_2_arr - date_1_arr

    # Write the output in GeoTIFF
    dst = rasterio.open(index_file_diff, "w", **profile)
    dst.write(diff_index,1)
    dst.close()
    
    print(f'A new {index_file_diff} file is created : {index_file_diff}')
    
else:
    print(f'--> {index_file_diff} - already exists')

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-5-8a422e9c361d> in <module>
      4 
      5 # Get the spectral indices associated with the dates you have chosen
----> 6 index_file_1 = glob.glob(f'{index_path}*{date_1}*.tif')[0]
      7 index_file_2 = glob.glob(f'{index_path}*{date_2}*.tif')[0]
      8 

IndexError: list index out of range