How to generate SSH key pairs with Python

Use cryptography! pycrypto is not in active development anymore and if possible you should be using cryptography. Since June it’s possible to generate SSH public keys as well:

from cryptography.hazmat.primitives import serialization as crypto_serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.backends import default_backend as crypto_default_backend

key = rsa.generate_private_key(
    backend=crypto_default_backend(),
    public_exponent=65537,
    key_size=2048
)

private_key = key.private_bytes(
    crypto_serialization.Encoding.PEM,
    crypto_serialization.PrivateFormat.PKCS8,
    crypto_serialization.NoEncryption()
)

public_key = key.public_key().public_bytes(
    crypto_serialization.Encoding.OpenSSH,
    crypto_serialization.PublicFormat.OpenSSH
)

Note: You need at least version 1.4.0.

Note: If your SSH client does not understand this private key format, replace PKCS8 with TraditionalOpenSSL.