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ASN.1 library for Python
------------------------
[PyPI]
[Python Versions]
[Build status]
[Coverage Status]
[GitHub license]
This is a free and open source implementation of ASN.1 types and codecs
as a Python package. It has been first written to support particular
protocol (SNMP) but then generalized to be suitable for a wide range
of protocols based on
[ASN.1 specification].
**NOTE:** The package is now maintained by *Christian Heimes* and
*Simon Pichugin* in project https://github.com/pyasn1/pyasn1.
Features
--------
* Generic implementation of ASN.1 types (X.208)
* Standards compliant BER/CER/DER codecs
* Can operate on streams of serialized data
* Dumps/loads ASN.1 structures from Python types
* 100% Python, works with Python 2.7 and 3.6+
* MT-safe
* Contributed ASN.1 compiler [Asn1ate]
Why using pyasn1
----------------
ASN.1 solves the data serialisation problem. This solution was
designed long ago by the wise Ancients. Back then, they did not
have the luxury of wasting bits. That is why ASN.1 is designed
to serialise data structures of unbounded complexity into
something compact and efficient when it comes to processing
the data.
That probably explains why many network protocols and file formats
still rely on the 30+ years old technology. Including a number of
high-profile Internet protocols and file formats.
Quite a number of books cover the topic of ASN.1.
[Communication between heterogeneous systems]
by Olivier Dubuisson is one of those high quality books freely
available on the Internet.
The pyasn1 package is designed to help Python programmers tackling
network protocols and file formats at the comfort of their Python
prompt. The tool struggles to capture all aspects of a rather
complicated ASN.1 system and to represent it on the Python terms.
How to use pyasn1
-----------------
With pyasn1 you can build Python objects from ASN.1 data structures.
For example, the following ASN.1 data structure:
```bash
Record ::= SEQUENCE {
id INTEGER,
room [0] INTEGER OPTIONAL,
house [1] INTEGER DEFAULT 0
}
```
Could be expressed in pyasn1 like this:
```python
class Record(Sequence):
componentType = NamedTypes(
NamedType('id', Integer()),
OptionalNamedType(
'room', Integer().subtype(
implicitTag=Tag(tagClassContext, tagFormatSimple, 0)
)
),
DefaultedNamedType(
'house', Integer(0).subtype(
implicitTag=Tag(tagClassContext, tagFormatSimple, 1)
)
)
)
```
It is in the spirit of ASN.1 to take abstract data description
and turn it into a programming language specific form.
Once you have your ASN.1 data structure expressed in Python, you
can use it along the lines of similar Python type (e.g. ASN.1
`SET` is similar to Python `dict`, `SET OF` to `list`):
```python
>>> record = Record()
>>> record['id'] = 123
>>> record['room'] = 321
>>> str(record)
Record:
id=123
room=321
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