diff --git a/reduction_tools/cat_lst.py b/reduction_tools/cat_lst.py
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+++ b/reduction_tools/cat_lst.py
@@ -0,0 +1,179 @@
+#!/usr/bin/python
+
+# author J.Beale
+
+"""
+# aim
+script to append lst files from different run locations
+so you give the script individual run numbers and/or 
+
+# usage
+python cat_lst.py -r <run_range> e.g. 45,50 - for runs 45-50, optional argument
+                  <a series of individual run numbers> e.g., 45 47 50 - for these specific runs
+                  #### note #### both of these can be used together - but you can't specify two lists
+                  -e endstation - "alvra" or "cristallina"
+                  -p pgroup
+                  -l label - i.e. 'light', 'dark' or 'both'
+                  -o output file name
+
+# output
+a concatentated list file of all the request runs
+"""
+
+import argparse
+import pandas as pd
+import glob
+import os
+import numpy as np
+
+def concatenate_files( input_file_lst, output ):
+
+    output_file = "{0}.lst".format( output )
+
+    # create output file
+    with open( output_file, "w" ) as output:
+
+        # loop through input list - read and write to output file
+        for lst_file_pwd in input_file_lst:
+            
+            # open and write to output file
+            with open( lst_file_pwd, "r" ) as lst_file:
+                output.write( lst_file.read() )
+
+def make_pwd( run_no, endstation, pgroup ):
+
+    # construct lst folder path
+    lst_pwd = "/sf/{0}/data/{1}/raw/".format( endstation, pgroup ) + "run" + run_no + "*/data"
+
+    return lst_pwd
+
+def find_lst( lst_dir, label ):
+
+    # if label = both, i.e. both lights and darks, set label to lst - so it's alwasy found
+    if label == "both":
+        label = "lst"
+
+    # create df for all lst
+    lst_dir_df = pd.DataFrame()
+
+    # search for lst with appropriate labels
+    for path, dirs, files in os.walk( lst_dir ):
+        for name in files:
+            if name.endswith( ".lst" ):
+
+                # get lst pwd
+                lst_pwd = os.path.join( path, name )
+
+                # put clen and stream pwd into df
+                data = [ {  "lst_pwd" : lst_pwd
+                         } ]
+                lst_dir_df_1 = pd.DataFrame( data )
+                lst_dir_df = pd.concat( ( lst_dir_df, lst_dir_df_1 ) )
+
+    # reset df index
+    lst_dir_df = lst_dir_df.reset_index( drop=True )
+
+    # return df lst from this directory
+    return lst_dir_df
+
+def generate_lst_df( run_lst, endstation, label, pgroup ):
+
+    # make run number df
+    cols = [ "run_no" ]
+    range_df = pd.DataFrame( run_lst, columns=cols )
+    # add zeros to left hand of number
+    range_df[ "run_no" ] = range_df.run_no.str.zfill(4)
+
+    # make new column of list paths
+    range_df[ "lst_app_dir" ] = range_df[ "run_no" ].apply( lambda x: make_pwd( x, endstation, pgroup ) )
+
+    # make df of lsts to be concatenated
+    lst_df = pd.DataFrame()
+
+    for index, row in range_df.iterrows():
+        
+        # get approximate dir pwd
+        lst_app_dir = row[ "lst_app_dir" ]
+        # find matching file
+        lst_dir = glob.glob( lst_app_dir )
+
+        # find lsts in lst directory depending on label
+        lst_dir_df = find_lst( lst_dir[0], label )
+
+        # append lst dir dfs
+        lst_df = pd.concat( [ lst_df, lst_dir_df ], ignore_index=True )
+    
+    # reset df index
+    lst_df = lst_df.reset_index( drop=True )
+
+    return lst_df
+
+def main( run_lst, endstation, label, pgroup, output_file ):
+
+    # make df of lst files
+    lst_df = generate_lst_df( run_lst, endstation, label, pgroup )
+
+    # concatinate all lst file in lst_df
+    concatenate_files( lst_df.lst_pwd, output_file )
+
+def range_of_runs(arg):
+    return list(map(int, arg.split(',')))
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "-r",
+        "--range",
+        help="list files in a range of run number to concatentate",
+        type=range_of_runs
+    )
+    parser.add_argument(
+        "runs",
+        help="type in indivdual run numbers for list to be concantenated",
+        type=str,
+        nargs='*',
+        default=[]
+        )
+    parser.add_argument(
+        "-e",
+        "--endstation",
+        help="which endstation did you collect these data from, e.g., alvra or cristallina",
+        type=str,
+        default="cristallina"
+        )
+    parser.add_argument(
+        "-p",
+        "--pgroup",
+        help="pgroup the data are collected in",
+        type=str
+        )
+    parser.add_argument(
+        "-l",
+        "--label",
+        help="the label of the lst file, i.e. 'light', 'dark' or 'both'",
+        type=str,
+        required=True
+        )
+    parser.add_argument(
+        "-o",
+        "--output",
+        help="name of output file",
+        type=str,
+        )
+    args = parser.parse_args()
+    # make continuous list from input range limits
+    range = []
+    if args.range is not None:
+        limits = args.range
+        range = np.arange( limits[0], limits[1]+1 )
+        # convert to list
+        range = range.tolist()
+        # convert to strings
+        range = list( map( str, range ) )
+    # concat range and run lists
+    runs = args.runs
+    run_lst = range + runs
+    print( "appending {0} lst files from runs {1}".format( args.label, run_lst ) )
+    # run main
+    main( run_lst, args.endstation, args.label, args.pgroup, args.output )
+    print( "done" )
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