Simple Python Port Scanner

#!/usr/bin/python
import sys,os
from socket import *
os.system('clear')

def about():
    print "###################################################"
    print "# Simple Port Scanner"
    print "# Coded By Pentest101"
    print "# Blog Pentest101.blogspot.com"
    print "#"
def usage():
    print "[?] usage : ./portScan.py 1 65500 IP --- All PORTS"
    print "[?] usage : ./portScan.py 21      IP --- Single PORT"

def main():
    if (int(len(sys.argv))==1):
        about()
        usage()

    if (int(len(sys.argv)) == 3):
        #one port
        about()
        try:socket(AF_INET, SOCK_STREAM).connect((sys.argv[2], int(sys.argv[1]))); print "[!] PORT : ", int(sys.argv[1])," OPEN"
        except: pass

    if (int(len(sys.argv)) == 4):
        #range
        about()
        port = 0
        for port in range( int(sys.argv[1]) , int(sys.argv[2]) ):
            try:socket(AF_INET, SOCK_STREAM).connect((sys.argv[3], port)); print "[!] PORT : ", port," OPEN"
            except: pass
main()
print "http://pentest101.blogspot.com"
print "###################################################"