Python has multiple excellent ASN.1 implementations (like pyasn1, asn1, and asn1tools), but these generally fall into the latter category: being written purely in Python makes performance a concern, and integration into a stack where other ASN.1 parsers are used (e.g., at the X.509 layer) introduces a differential risk. DER is a self-describing and self-delimiting encoding: A given DER message can be fully and soundly parsed without prior reference to a schema or format description beyond the encoding rules of DER themselves. Modernization: dataclasses and dataclass -style declarative APIs have taken the Python ecosystem by storm, and for good reason: they’re uniform, integrate cleanly with type checkers, and define types as code rather than as data.