GRAI

class epc.schemes.GRAI(*args, **kwargs)

The Global Returnable Asset Identifier EPC scheme is used to assign a unique identity to a specific returnable asset, such as a reusable shipping container or a pallet skid.

General syntax: urn:epc:id:grai:CompanyPrefix.AssetType.SerialNumber

Example: urn:epc:id:grai:0614141.12345.400

filter(tag_filter)

The filter value is additional control information that may be included in the EPC memory bank of a Gen 2 tag. The intended use of the filter value is to allow an RFID reader to select or deselect the tags corresponding to certain physical objects, to make it easier to read the desired tags in an environment where there may be other tags present in the environment. For example, if the goal is to read the single tag on a pallet, and it is expected that there may be hundreds or thousands of item-level tags present, the performance of the capturing application may be improved by using the Gen 2 air interface to select the pallet tag and deselect the item-level tags.

Allowed values for GRAI tags:

Value

Constant

Description

0

FILTER_ALL

All Others

1-7

FILTER_RESERVED_*

Reserved
Parameters

tag_filter (int) – The filter value, defaults to FILTER_ALL.

Raises

AttributeError – Filter must be between 0 and 7.

Returns

The GRAI tag object.

Return type

epc.schemes.GRAI

company_prefix(company_prefix, company_prefix_length=None)

The GS1 Company Prefix, assigned by GS1 to a managing entity.

Length corresponds to the number of digits in the company prefix.

Parameters

  • company_prefix (str, int) – GS1 company prefix.

  • company_prefix_length (int, optional) – Number of digits in the company prefix. Required when company_prefix is an int.

Returns

The GRAI tag object.

Return type

epc.schemes.GRAI

asset_type(asset_type)

The Asset Type, assigned by the managing entity to a particular class of asset.

Parameters

asset_type (int, str) – The asset type.

Raises

ValueError – Unable to convert input to an integer.

Returns

The GRAI tag object.

Return type

epc.schemes.GRAI

serial_number(serial_number)

The Serial Number, assigned by the managing entity to an individual object. Because an EPC always refers to a specific physical object rather than an asset class, the serial number is mandatory in the GRAI-EPC.

Parameters

serial_number (str, int) – The serial number.

Raises

  • AttributeError – Serial number bit length incorrect.

  • AttributeError – Serial number length incorrect.

Returns

The GRAI tag object.

Return type

epc.schemes.GRAI

tag_size()

Set the size for the tag. Options are SIZE_96 or SIZE_170.

Parameters

tag_size (int) – Tag size in bits. Defaults to SIZE_96.

Raises

AttributeError – Invalid tag size specified.

Returns

The GRAI tag object.

Return type

epc.schemes.GRAI

property tag_uri
Returns

The tag’s URI.

Return type

str

property pure_identity_uri
Returns

The tag’s pure identity URI.

Return type

str

property barcode
Returns

The barcode representation of the tag.

Return type

str

property barcode_humanized
Returns

A human readable barcode representation of the tag.

Return type

str

property values
Returns

Dictionary containing:

  • size (int): the tag’s size in bits

  • filter (int)

  • company_prefix (str)

  • asset_type (int)

  • serial_number (int or str)

decode_epc(hex_string)

Decode an encoded tag and populate this object’s values from it.

Parameters

hex_string (str) – Tag data encoded as a hexadecimal string.

Raises

  • ValueError – EPC scheme header does not match input.

  • ValueError – Filter does not match allowed values.

  • ValueError – Supplied hex_string bit length invalid.

decode_barcode(barcode, company_prefix_length)

Decode a barcode and populate this object’s values from it.

Parameters

  • hex_string (str) – Barcode

  • company_prefix_length (int) – Number of digits of the company prefix length

Raises

  • ValueError – Expected barcode header does not match input.

  • AttributeError – Invalid barcode length, or wrong company prefix.

check_fields()

Checks to make sure all components of the tag are present, including size, filter, company_prefix, asset_type and serial_number.

Raises

AttributeError – If any components of the tag are missing.

Hint

To get the encoded tag data, use python’s built in conversion methods:

>>> tag = GRAI().tag_size(GRAI.SIZE_170)
>>> tag.company_prefix('000123').asset_type(8).serial_number('ABC')

# Hexadecimal
>>> hex(tag)
'0x3718001ec0000220c286000000000000000000000000'

# Binary
>>> bin(tag)
'0b110111000110000000000000011110110000000000000000000010001000001100001010000110000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'

Constants

Filters

GRAI.FILTER_ALL
GRAI.FILTER_RESERVED_*

Replace asterisk with 1-7.

Sizes

GRAI.SIZE_96

96 bit tag size.

GRAI.SIZE_170

170 bit tag size.

Headers

GRAI.HEADER_BARCODE

GS1 specified barcode header: 8003.

GRAI.HEADER_96

GS1 specified hexadecimal header for 96 bit GRAI tags: 0x33.

GRAI.HEADER_170

GS1 specified hexadecimal header for 202 bit GRAI tags: 0x37.

GRAI.GRAI_96

Human readable GS1 specified header for 96 bit GRAI tags: grai-96.

GRAI.GRAI_170

Human readable GS1 specified header for 202 bit GRAI tags: grai-170.