from M2Crypto import RSA,BIO

  fp = file('rsa_pub.pem','rb');
  pub_key_str = fp.read();
  fp.close();

  mb = BIO.MemoryBuffer(pub_key_str);
  pub_key = RSA.load_pub_key_bio(mb);

  data = '12345678';
  en_data = pub_key.public_encrypt(data,RSA.pkcs1_padding);

  ...

from M2Crypto import RSA,BIO

  private_key_str = file('rsa_private.pem','rb').read();
  private_key = RSA.load_key_string(private_key_str);
  data = 'sdfdjslfjaskldfjdsklfjsd';
  de_data = private_key.private_decrypt(data,RSA.pkcs1_padding);