import os
import glob
import csv

# import csv files from folder and change directory
path = r'file_path'
#os.chdir(path)

# create list of all files in directory
allFiles = glob.glob(path + "/*.csv")
print(allFiles)

# read in each file, add filename column
with open('output.csv', 'w') as csvoutput:
   for i, fname in enumerate(allFiles):
       print(fname)
       with open(fname,'r') as csvinput:
           reader = csv.reader(csvinput)
           all = []
           if i == 0:
               row = next(reader)
               row.append('FileName')
               all.append(row)
           else:
               next(reader)
           writer = csv.writer(csvoutput, lineterminator='\n')
           print(os.path.basename(csvinput.name))

           for row in reader:
               row.append(os.path.basename(csvinput.name))
               all.append(row)
           writer.writerows(all)