Data Attributes

The attribute operator (.) can be used to recursively resolve values from a compound native Python data type such as an object or dictionary. This can be used when the thing which the rule is evaluating has members with their own submembers. If the resolver function fails, the attribute will be checked to determine if it is a builtin attribute.

Builtin Attributes

The following attributes are builtin to the default Context object.

Attribute Name	Attribute Type
ARRAY Attributes
ends_with(prefix)	FUNCTION
is_empty	BOOLEAN
length	FLOAT
starts_with(prefix)	FUNCTION
to_ary	ARRAY
to_set	SET
BYTES Attributes
ends_with(prefix)	FUNCTION
is_empty	BOOLEAN
length	FLOAT
starts_with(prefix)	FUNCTION
to_ary	ARRAY
to_set	SET
decode(encoding)	FUNCTION
DATETIME Attributes
date	DATETIME
day	FLOAT
hour	FLOAT
microsecond	FLOAT
millisecond	FLOAT
minute	FLOAT
month	FLOAT
second	FLOAT
to_epoch	FLOAT
weekday	STRING
year	FLOAT
zone_name	STRING
FLOAT Attributes 1
ceiling	FLOAT
floor	FLOAT
is_nan	BOOLEAN
to_flt	FLOAT
to_str	STRING
MAPPING Attributes
is_empty	BOOLEAN
keys	ARRAY
length	FLOAT
values	ARRAY
SET Attributes
is_empty	BOOLEAN
length	FLOAT
to_ary	ARRAY
to_set	SET
STRING Attributes
as_lower	STRING
as_upper	STRING
encode(encoding)	FUNCTION
ends_with(prefix)	FUNCTION
to_ary	ARRAY
to_flt	FLOAT
to_set	SET
to_str	STRING
to_int	FLOAT
is_empty	BOOLEAN
length	FLOAT
starts_with(prefix)	FUNCTION
TIMEDELTA Attributes
days	FLOAT
seconds	FLOAT
microseconds	FLOAT
total_seconds	FLOAT

FLOAT Attributes ¹

Due to the syntax of floating point literals, the attributes must be accessed using parenthesis. For example 3.14.to_str is invalid while (3.14).to_str is valid.

Encoding and Decoding

BYTES values can be converted to STRING values by calling their .decode method. STRING values can be converted to BYTES values by calling their .encode method. This resembles Python’s native functionality and the encoding argument to each is the same, i.e. it can be any encoding name that Python can handle such as UTF-8. In addition to the encoding names that Python can handle, the special names hex, base16 and base64 can be used for transcoding ascii-hex, and base-64 formatted data.

OBJECT Attribute Access

Added in version 5.0.0.

Attributes on OBJECT values are resolved differently from the builtin attributes listed above. Instead of using the builtin attribute resolver, the engine checks the attribute name against the OBJECT’s declared schema at parse time. If the attribute is not in the schema, an ObjectAttributeError is raised immediately with a suggestion for the closest valid attribute name.

At evaluation time, the value is fetched using the OBJECT type’s accessor callable, which defaults to getattr(). This means the builtin attribute resolvers (length, as_upper, etc.) do not apply to OBJECT values - only the attributes declared in the schema are accessible. The symbol resolver fallback used by MAPPING values is also bypassed entirely for OBJECT types.

Object Methods

Much like in Python, a method is a function that is associated with an object. They are defined as FUNCTION values and are accessed as attributes.

BYTES decode(STRING encoding) -> STRING

returns:

STRING

encoding:

(STRING) The encoding name to use.

Returns the decoded value.

Added in version 4.5.0.

STRING encode(STRING encoding) -> BYTES

returns:

BYTES

encoding:

(STRING) The encoding name to use.

Returns the encoded value.

Added in version 4.5.0.

ARRAY | BYTES | STRING ends_with(ARRAY | BYTES | STRING suffix) -> BOOLEAN

returns:

BOOLEAN

suffix:

The suffix to check for. The data type must match the object type.

Check whether the value ends with the specified value.

Added in version 4.5.0.

ARRAY | BYTES | STRING starts_with(ARRAY | BYTES | STRING prefix) -> BOOLEAN

returns:

BOOLEAN

prefix:

The prefix to check for. The data type must match the object type.

Check whether the value starts with the specified value.

Added in version 4.5.0.