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Parses ASN.1 value notation into a Python object or JSON without requiring its ASN.1 schema.

Project description

asn1vnparser Documentation Status

Parses ASN.1 value notation into a Python object or JSON without requiring its ASN.1 schema.


  • Parsing ASN.1 value notation into a Python object, or a JSON string
  • No ASN.1 Schema Required


  • Since Knowledge of schema is not used, misdetection of ASN.1 types can occur; see Type Translations section.
  • Some ASN.1 types and grammars are not supported; see

Type Translations

asn1vnparser performs the following type translations:

ASN.1 Type Python Type JSON Type Example (ASN.1 -> Python)
NULL None null NULL -> None
BOOLEAN bool True/False TRUE -> True
INTEGER int number (int) 3 -> 3
REAL float number (real) 0.1 -> 0.1
BIT STRING (^1) bitarray.bitarray string (e.g. “010101”) ‘010101’B -> bitarray.bitarray(‘010101’)
OCTET STRING (^1) bytes string (e.g. “0123ab”) ‘0123AB’H -> b’x01x23xab’
cstring (PrintableString, etc.) str string “foobar” -> ‘foobar’
ENUMERATED str string any-identifier -> ‘any-identifier’
CHOICE Dict[str, Any] {“string”: (any JSON object)} alt1 : 123 -> {‘alt1’: 123}
Open Type (e.g. type field) Dict[str, Any] {“String”: (any JSON object)} Type1 : 123 -> {‘Type1’: 123}
empty SEQUENCE or SEQUENCE OF {} (empty dict) {} (empty object) {} -> {}, [] -> {}
SEQUENCE dict object {f1 val, f2 1} -> {‘f1’: ‘val’, ‘f2’: 1}
SEQUENCE OF list array [1, 2, 3] -> [1, 2, 3]
OBJECT IDENTIFIER List[int] array of number (int) {1 2 3} -> [1, 2, 3]

(^1) CONTAINING (some_value) is interpreted as simply (some_value), e.g.:

    field1 123,
    field2 CONTAINING {
        field2-1 TRUE,
        field2-2 FALSE

is parsed into following Python object:

    "field1": 123,
    "field2": {
        "field2-1": True,
        "field2-2": False


This package was created with Cookiecutter and the audreyr/cookiecutter-pypackage project template.


0.2.1 (2021-11-14)

  • Disable pyparsing v3, which breaks tests
  • Update license to ISC

0.2.0 (2019-10-02)

New Features

  • Partial parsing of a value or a value assignment (parse_all option)
>>> parse_asn1_value(
...     "alt1: enum1\n---this is remaining string---",
...     as_json=True,
...     parse_all=False)  # as_json
('{"alt1": "enum1"}', '\n---this is remaining string---')
  • Parsing multiple value assignments
>>> parse_asn1_value_assignments(
...     'value1 INTEGER ::= 1\nvalue2 Type2 ::= the-value')
    {'value_name': 'value1', 'type_name': 'INTEGER', 'value': 1},
    {'value_name': 'value2', 'type_name': 'Type2', 'value': 'the-value'}

Bug Fixes

  • CLI no longer crashes when given --json option.

0.1.0 (2019-09-29)

  • First release on PyPI.

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