if len(sys.argv) < 2:
    print('You need an argument.')
sys.exit(0)
var = sys.argv[1]
for root, dirs, files in os.walk('.'):
    for f in files:
        if var in f:
            fullname = os.path.join(root, f)
print(os.path.abspath(fullname))
Make a file searching program that accepts a single regular expression with sys.argv.