python extract public key from pem format publi key.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import sys
from Crypto.PublicKey import RSA

def main(argv):
    finput = open(argv[1], 'r')
    rsa=RSA.importKey(finput) # there could import public key.
    output=argv[2]
    with open(output, 'wb') as f:
        f.write(rsa.exportKey('DER'))
if __name__ == '__main__':
    sys.exit(main(sys.argv))

　　Now, openssl command line only can extract public key from private key.

So ther I provide scripts extract der format public key from pem public key.

python extract_pub_key.py test_pub.pem test_pub.der