>>> from Crypto.Cipher import PKCS1_v1_5
>>> from Crypto.PublicKey import RSA
>>> from Crypto.Hash import SHA
>>>
>>> message = b'To be encrypted'
>>> h = SHA.new(message)
>>>
>>> key = RSA.importKey(open('pubkey.der').read())
>>> cipher = PKCS1_v1_5.new(key)
>>> ciphertext = cipher.encrypt(message+h.digest())