Null type¶
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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: Raises: : :py:class:`pyasn1.error.PyAsn1Error` – On constraint violation or bad initializer.
Note
The Null type models ASN.1 NULL.
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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- value (
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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’sTagSet
, then use the result as new object’s ASN.1 tag(s). - explicitTag (
Tag
) – Explicitly apply given ASN.1 tag object to caller’sTagSet
, then use the result as new object’s ASN.1 tag(s).
Returns: Null
– new instance of NULL type/value- value (
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tagSet
= TagSet((), Tag(tagClass=0, tagFormat=0, tagId=5))¶ Set (on class, not on instance) or return a
TagSet
object representing ASN.1 tag(s) associated with Null type.
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effectiveTagSet
¶ For Null type is equivalent to tagSet
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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.
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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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isValue
¶ Indicate if Null object represents ASN.1 type or ASN.1 value.
In other words, if isValue is True, then the ASN.1 object is initialized.
Returns: bool
–True
if object represents ASN.1 value and type,False
if object represents just ASN.1 type.Note
There is an important distinction between PyASN1 type and value objects. The PyASN1 type objects can only participate in ASN.1 type operations (subtyping, comparison etc) and serve as a blueprint for serialization codecs to resolve ambiguous types.
The PyASN1 value objects can additionally participate in most of built-in Python operations.
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