Deprecated since 3.7. The option is deprecated since OpenSSL 1.1.0. It was added to 2.7.15 and 3.6.3 for backwards compatibility with OpenSSL 1.0.2.
Prevents a TLSv1.3 connection. This option is only applicable in conjunction with PROTOCOL_TLS. It prevents the peers from choosing TLSv1.3 as the protocol version. TLS 1.3 is available with OpenSSL 1.1.1 or later. When Python has been compiled against an older version of OpenSSL, the flag defaults to 0.