Sequence type

class pyasn1.type.univ.Sequence(componentType=None, tagSet=tagSet(), subtypeSpec=ConstraintsIntersection(), sizeSpec=ConstraintsIntersection())

Create Sequence type.

Sequence objects are mutable and duck-type Python dict objects.

Keyword Arguments:
 
  • componentType (NamedType) – Object holding named ASN.1 types allowed within this collection
  • tagSet (TagSet) – Object representing non-default ASN.1 tag(s)
  • subtypeSpec (ConstraintsIntersection) – Object representing non-default ASN.1 subtype constraint(s)
  • sizeSpec (ConstraintsIntersection) – Object representing collection size constraint

Examples

class Description(Sequence):  #  Set is similar
    '''
    ASN.1 specification:

    Description ::= SEQUENCE {
        surname    IA5String,
        first-name IA5String OPTIONAL,
        age        INTEGER DEFAULT 40
    }
    '''
    componentType = NamedTypes(
        NamedType('surname', IA5String()),
        OptionalNamedType('first-name', IA5String()),
        DefaultedNamedType('age', Integer(40))
    )

descr = Description()
descr['surname'] = 'Smith'
descr['first-name'] = 'John'

Note

The Sequence type models a collection of named ASN.1 components. Ordering of the components is preserved upon de/serialisation.

clone(componentType=None, tagSet=tagSet(), subtypeSpec=ConstraintsIntersection())

Create a modified version of Sequence schema object.

The clone() method accepts the same set arguments as Sequence class takes on instantiation except that all arguments of the clone() method are optional.

Whatever arguments are supplied, they are used to create a copy of self taking precedence over the ones used to instantiate self.

Possible values of self are never copied over thus clone() can only create a new schema object.

Returns:new instance of Sequence type/value

Note

Due to the mutable nature of the Sequence object, even if no arguments are supplied, new Sequence object will always be created as a shallow copy of self.

subtype(componentType=None, implicitTag=Tag(), explicitTag=Tag(), subtypeSpec=ConstraintsIntersection())

Create a specialization of Sequence schema object.

The subtype() method accepts the same set arguments as Sequence class takes on instantiation except that all parameters of the subtype() method are optional.

With the exception of the arguments described below, the rest of supplied arguments they are used to create a copy of self taking precedence over the ones used to instantiate self.

The following arguments to subtype() create a ASN.1 subtype out of Sequence type.

Other Parameters:
 
  • implicitTag (Tag) – Implicitly apply given ASN.1 tag object to self’s TagSet, then use the result as new object’s ASN.1 tag(s).
  • explicitTag (Tag) – Explicitly apply given ASN.1 tag object to self’s TagSet, then use the result as new object’s ASN.1 tag(s).
  • subtypeSpec (ConstraintsIntersection) – Add ASN.1 constraints object to one of the self’s, then use the result as new object’s ASN.1 constraints.
Returns:

new instance of Sequence type/value

Note

Due to the immutable nature of the Sequence object, if no arguments are supplied, no new Sequence object will be created and self will be returned instead.

tagSet = <TagSet object at 0x10511bf60 tags 0:32:16>

Set (on class, not on instance) or return a TagSet object representing ASN.1 tag(s) associated with Sequence type.

subtypeSpec = <ConstraintsIntersection object>

Set (on class, not on instance) or return a ConstraintsIntersection object imposing constraints on Sequence type initialization values.

sizeSpec = <ConstraintsIntersection object>

Default ConstraintsIntersection object imposing constraints on Sequence objects

componentType = <NamedTypes object at 0x1051260f0 types >

Default collection of ASN.1 types of component (e.g. NamedType) object imposing size constraint on Sequence objects

effectiveTagSet

For Sequence type is equivalent to tagSet

getComponentByName(name, default=<NoValue object at 4379922896>, instantiate=True)

Returns Sequence type component by name.

Equivalent to Python dict subscription operation (e.g. []).

Parameters:

name (str) – Sequence type component name

Keyword Arguments:
 
  • default (object) – If set and requested component is a schema object, return the default object instead of the requested component.
  • instantiate (bool) – If True (default), inner component will be automatically instantiated. If ‘False’ either existing component or the noValue object will be returned.
Returns:

PyAsn1Item – Instantiate Sequence component type or return existing component value

getComponentByPosition(idx, default=<NoValue object at 4379922896>, instantiate=True)

Returns Sequence type component by index.

Equivalent to Python sequence subscription operation (e.g. []).

Parameters:

idx (int) – Component index (zero-based). Must either refer to an existing component or (if componentType is set) new ASN.1 schema object gets instantiated.

Keyword Arguments:
 
  • default (object) – If set and requested component is a schema object, return the default object instead of the requested component.
  • instantiate (bool) – If True (default), inner component will be automatically instantiated. If ‘False’ either existing component or the noValue object will be returned.
Returns:

PyAsn1Item – a PyASN1 object

Examples

# can also be Set
class MySequence(Sequence):
    componentType = NamedTypes(
        NamedType('id', OctetString())
    )

s = MySequence()

# returns component #0 with `.isValue` property False
s.getComponentByPosition(0)

# returns None
s.getComponentByPosition(0, default=None)

s.clear()

# returns noValue
s.getComponentByPosition(0, instantiate=False)

# sets component #0 to OctetString() ASN.1 schema
# object and returns it
s.getComponentByPosition(0, instantiate=True)

# sets component #0 to ASN.1 value object
s.setComponentByPosition(0, 'ABCD')

# returns OctetString('ABCD') value object
s.getComponentByPosition(0, instantiate=False)

s.clear()

# returns noValue
s.getComponentByPosition(0, instantiate=False)
isSameTypeWith(other, matchTags=True, matchConstraints=True)

Examine Sequence type for equality with other ASN.1 type.

ASN.1 tags (tag) and constraints (constraint) are examined when carrying out ASN.1 types comparison.

Python class inheritance relationship is NOT considered.

Parameters:other (a pyasn1 type object) – Class instance representing ASN.1 type.
Returns:boolTrue if other is Sequence type, False otherwise.
isSuperTypeOf(other, matchTags=True, matchConstraints=True)

Examine Sequence type for subtype relationship with other ASN.1 type.

ASN.1 tags (tag) and constraints (constraint) are examined when carrying out ASN.1 types comparison.

Python class inheritance relationship is NOT considered.

Parameters:other (a pyasn1 type object) – Class instance representing ASN.1 type.
Returns:boolTrue if other is a subtype of Sequence type, False otherwise.
isValue

Indicate that Sequence object represents ASN.1 value.

If isValue is False then this object represents just ASN.1 schema.

If isValue is True then, in addition to its ASN.1 schema features, this object can also be used like a Python built-in object (e.g. int, str, dict etc.).

Returns:boolFalse if object represents just ASN.1 schema. True if object represents ASN.1 schema and can be used as a normal value.

Note

There is an important distinction between PyASN1 schema and value objects. The PyASN1 schema objects can only participate in ASN.1 schema-related operations (e.g. defining or testing the structure of the data). Most obvious uses of ASN.1 schema is to guide serialisation codecs whilst encoding/decoding serialised ASN.1 contents.

The PyASN1 value objects can additionally participate in many operations involving regular Python objects (e.g. arithmetic, comprehension etc).

setComponentByName(name, value=<NoValue object at 4379922896>, verifyConstraints=True, matchTags=True, matchConstraints=True)

Assign Sequence type component by name.

Equivalent to Python dict item assignment operation (e.g. []).

Parameters:

name (str) – Sequence type component name

Keyword Arguments:
 
  • value (object or PyAsn1Item derivative) – A Python value to initialize Sequence component with (if componentType is set) or ASN.1 value object to assign to Sequence component.
  • verifyConstraints (bool) – If False, skip constraints validation
  • matchTags (bool) – If False, skip component tags matching
  • matchConstraints (bool) – If False, skip component constraints matching
Returns:

self

setComponentByPosition(idx, value=<NoValue object at 4379922896>, verifyConstraints=True, matchTags=True, matchConstraints=True)

Assign Sequence type component by position.

Equivalent to Python sequence item assignment operation (e.g. []).

Parameters:

idx (int) – Component index (zero-based). Must either refer to existing component (if componentType is set) or to N+1 component otherwise. In the latter case a new component of given ASN.1 type gets instantiated and appended to Sequence sequence.

Keyword Arguments:
 
  • value (object or PyAsn1Item derivative) – A Python value to initialize Sequence component with (if componentType is set) or ASN.1 value object to assign to Sequence component.
  • verifyConstraints (bool) – If False, skip constraints validation
  • matchTags (bool) – If False, skip component tags matching
  • matchConstraints (bool) – If False, skip component constraints matching
Returns:

self

tagMap

Return a TagMap object mapping ASN.1 tags to ASN.1 objects within callee object.