from sys import argv, exit
import re
if len(argv) < 2:
    print("mising command-line argument")
    exit(1)

pattern1 = re.compile(r'AGAT')
pattern2 = re.compile(r'AATG')
pattern3 = re.compile(r'TATC')

with open(argv[1], "r") as f:
    count = 0
    contents = f.read()
    print(contents)
    print(contents[0:4])
    i = 0
    j = i + 4
    while contents[i:j]: # will read contents until end of file
        span = contents[i:j]
        while contents[i+4:j+4] == span:
            count += 1
            print("span reapeats " + str(count) + " times" )
            i += 4
            j += 4