Null type

class pyasn1.type.univ.Null(value=NoValue(), tagSet=TagSet())

Create Null type or object.

Null objects are immutable and duck-type Python str objects (always empty).

Parameters:

• value (str or Null object) – Python empty string literal or Null class instance.
• tagSet (TagSet) – Object representing non-default ASN.1 tag(s)

Raises:

: :py:class:`pyasn1.error.PyAsn1Error` – On constraint violation or bad initializer.

Note

The Null type models ASN.1 NULL.

clone(value=NoValue(), tagSet=TagSet())

Create a copy of a Null type or object.

Any parameters to the clone() method will replace corresponding properties of the Null object.

Parameters:

• value (str or Null object) – Initialization value to pass to new ASN.1 object instead of inheriting one from the caller.
• tagSet (TagSet) – Object representing ASN.1 tag(s) to use in new object instead of inheriting from the caller

Returns:

Null – new instance of NULL type/value

subtype(value=NoValue(), implicitTag=Tag(), explicitTag=Tag())

Create a copy of a Null type or object.

Any parameters to the subtype() method will be added to the corresponding properties of the Null object.

Parameters:

• value (int, str or Null object) – Initialization value to pass to new ASN.1 object instead of inheriting one from the caller.
• implicitTag (Tag) – Implicitly apply given ASN.1 tag object to caller’s TagSet, then use the result as new object’s ASN.1 tag(s).
• explicitTag (Tag) – Explicitly apply given ASN.1 tag object to caller’s TagSet, then use the result as new object’s ASN.1 tag(s).

Returns:

Null – new instance of NULL type/value

tagSet = TagSet((), Tag(tagClass=0, tagFormat=0, tagId=5))

Default TagSet object for ASN.1 Null objects

hasValue()

Indicate if Null object represents ASN.1 value or ASN.1 type.

The PyASN1 type objects can only participate in types comparison and serve as a blueprint for serialization codecs to resolve ambiguous types.

The PyASN1 value objects can additionally participate to most of built-in Python operations.

Returns:bool – True if object is ASN.1 value, False otherwise.

isSameTypeWith(other, matchTags=True, matchConstraints=True)

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

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

No Python inheritance relationship between PyASN1 objects is considered.

Parameters:other (a pyasn1 type object) – Class instance representing ASN.1 type. Returns:bool – True if other is Null type, False otherwise.

isSuperTypeOf(other, matchTags=True, matchConstraints=True)

Examine Null 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.

No Python inheritance relationship between PyASN1 objects is considered.

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

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