f = pd.read_csv(file, index_col=0)
f.loc[:, ('Vehicle')] = filenamearray[0].replace('veh', '')
f.loc[:, ('Year')] = filenamearray[1].replace('year', '')
if 'timelimit' in file:
    f.loc[:, ('Timelimit')] = '1'
else:
    f.loc[:, ('Timelimit')] = '0'
df_list.append(f)
merged = pd.concat(df_list, axis=0)
merged.to_csv('merged.csv')
Concatenating a large number of CSV files (30,000) in in Python Pandas