Help Center> Object Storage Service> Python> Object-Related APIs (SDK for Python)> Modifying Object Metadata (SDK for Python)
Updated on 2024-06-19 GMT+08:00

Modifying Object Metadata (SDK for Python)

Function

Object metadata is a set of name-value pairs that describe the object and is used for object management.

Currently, only the system-defined metadata can be modified.

System-defined metadata consists of system-controlled metadata and user-controlled metadata. The kind of metadata like Last-Modified is controlled by the system and cannot be modified. However, the kind of metadata configured for objects such as ContentLanguage can be modified by calling APIs.

This API modifies, deletes, or adds metadata to objects in a bucket.

Restrictions

  • To configure object metadata, you must be the bucket owner or have the required permission (obs:object:ModifyObjectMetaData in IAM or ModifyObjectMetaData in a bucket policy). For details, see Introduction to OBS Access Control, IAM Custom Policies, and Configuring an Object Policy.
  • The mapping between OBS regions and endpoints must comply with what is listed in Regions and Endpoints.
  • If versioning is enabled for a bucket, you can set metadata for objects of the latest version, but cannot set metadata for objects of historical versions.
  • You cannot set metadata for Archive objects.

Method

ObsClient.setObjectMetadata(bucketName, objectKey, metadata, headers, versionId)

Request Parameters

Table 1 List of request parameters

Parameter

Type

Mandatory (Yes/No)

Description

bucketName

str

Yes

Explanation:

Bucket name

Restrictions:

  • A bucket name must be unique across all accounts and regions.
  • A bucket name:
    • Must be 3 to 63 characters long and start with a digit or letter. Lowercase letters, digits, hyphens (-), and periods (.) are allowed.
    • Cannot be formatted as an IP address.
    • Cannot start or end with a hyphen (-) or period (.).
    • Cannot contain two consecutive periods (..), for example, my..bucket.
    • Cannot contain periods (.) and hyphens (-) adjacent to each other, for example, my-.bucket or my.-bucket.
  • If you repeatedly create buckets of the same name in the same region, no error will be reported and the bucket properties comply with those set in the first creation request.

Default value:

None

objectKey

str

Yes

Explanation:

Object name. An object is uniquely identified by an object name in a bucket. An object name is a complete path that does not contain the bucket name.

For example, if the address for accessing the object is examplebucket.obs.ap-southeast-1.myhuaweicloud.com/folder/test.txt, the object name is folder/test.txt.

Value range:

The value must contain 1 to 1,024 characters.

Default value:

None

metadata

dict

No

Explanation:

Custom metadata of the object. You can add a header starting with x-obs-meta- in the request to define metadata. The custom metadata will be returned in the response when you retrieve the object or query the object metadata.

Restrictions:

  • The custom metadata cannot exceed 8 KB. To measure the custom metadata, sum the number of bytes in the UTF-8 encoding of each key and value.
  • The custom metadata keys are case insensitive, but are stored in lowercase in OBS. The key values are case sensitive.
  • Both custom metadata keys and their values must conform to US-ASCII standards. If non-ASCII or unrecognizable characters are required, they must be encoded or decoded in URL or Base64 on the client, because the server does not perform such operations.

Default value:

None

headers

SetObjectMetadataHeader

No

Explanation:

Request headers for configuring object metadata. For details, see Table 2.

versionId

str

No

Explanation:

Object version ID, for example, G001117FCE89978B0000401205D5DC9A

Value range:

The value must contain 32 characters.

Default value:

None

Table 2 SetObjectMetadataHeader

Parameter

Type

Mandatory (Yes/No)

Description

removeUnset

bool

No

Explanation:

Used to set the metadata operation indicator

Value range:

True: The metadata operation indicator is REPLACE. REPLACE uses the complete header carried in the current request to replace the original one and deletes the metadata that is not specified.

False: The metadata operation indicator is REPLACE_NEW. REPLACE_NEW replaces the metadata that already has a value, assigns a value to the metadata that does not have a value, and retains the metadata that is not specified.

Default value:

False

location

str

No

Explanation:

If the bucket is configured with website hosting, the request for obtaining the object can be redirected to another object in the bucket or an external URL.

The request is redirected to object anotherPage.html in the same bucket:

WebsiteRedirectLocation:/anotherPage.html

The request is redirected to an external URL http://www.example.com/:

WebsiteRedirectLocation:http://www.example.com/

OBS obtains the specified value from the header and stores it in the object metadata WebsiteRedirectLocation.

Restrictions:

  • The value must start with a slash (/), http://, or https:// and cannot exceed 2 KB.
  • OBS only supports redirection for objects in the root directory of a bucket.

Default value:

None

cacheControl

str

No

Explanation:

Cache-Control header in the response. It specifies the cache behavior of the web page when an object is downloaded.

Default value:

None

contentDisposition

str

No

Explanation:

Content-Disposition header in the response It specifies the name of an object when it is downloaded.

Default value:

None

contentEncoding

str

No

Explanation:

Content-Encoding header in the response It specifies the content encoding format when an object is downloaded.

Default value:

None

contentLanguage

str

No

Explanation:

Content-Language header in the response It specifies the content language format when an object is downloaded.

Default value:

None

contentType

str

No

Explanation:

Content-Type header in the response. It specifies the file type of an object when it is downloaded.

Default value:

None

expires

str

No

Explanation:

Expires header in the response. It specifies the cache expiration time of the web page when the object is downloaded.

CAUTION:

This parameter cannot be used to configure the expiration time of an object. To configure the object expiration time, see Setting an Object Expiration Time (SDK for Python).

Default value:

None

storageClass

str

No

Explanation:

Storage classes

Value range:

See Table 3.

Default value:

None

Table 3 StorageClass

Parameter

Type

Description

STANDARD

Standard storage class

Explanation:

Features low access latency and high throughput and is used for storing massive, frequently accessed (multiple times a month) or small objects (< 1 MB) requiring quick response.

WARM

Infrequent Access storage class

Explanation:

Used for storing data that is semi-frequently accessed (fewer than 12 times a year) but is instantly available when needed.

COLD

Archive storage class

Explanation:

Used for storing rarely accessed (once a year) data.

Responses

Table 4 List of returned results

Type

Description

GetResult

Explanation:

SDK common results

Table 5 GetResult

Parameter

Type

Description

status

int

Explanation:

HTTP status code

Value range:

A status code is a group of digits ranging from 2xx (indicating successes) to 4xx or 5xx (indicating errors). It indicates the status of a response. For more information, see Status Code.

Default value:

None

reason

str

Explanation:

Reason description.

Default value:

None

errorCode

str

Explanation:

Error code returned by the OBS server. If the value of status is less than 300, this parameter is left blank.

Default value:

None

errorMessage

str

Explanation:

Error message returned by the OBS server. If the value of status is less than 300, this parameter is left blank.

Default value:

None

requestId

str

Explanation:

Request ID returned by the OBS server

Default value:

None

indicator

str

Explanation:

Error indicator returned by the OBS server.

Default value:

None

hostId

str

Explanation:

Requested server ID. If the value of status is less than 300, this parameter is left blank.

Default value:

None

resource

str

Explanation:

Error source (a bucket or an object). If the value of status is less than 300, this parameter is left blank.

Default value:

None

header

list

Explanation:

Response header list, composed of tuples. Each tuple consists of two elements, respectively corresponding to the key and value of a response header.

Default value:

None

body

object

Explanation:

Result content returned after the operation is successful. If the value of status is larger than 300, this parameter value is null. The value varies with the API being called. For details, see Bucket-Related APIs (SDK for Python) and Object-Related APIs (SDK for Python).

Default value:

None

Code Examples

This example configures the object metadata.

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from obs import SetObjectMetadataHeader
from obs import ObsClient
import os
import traceback

# Obtain an AK and SK pair using environment variables or import the AK and SK pair in other ways. Using hard coding may result in leakage.
# Obtain an AK and SK pair on the management console. For details, see https://support.huaweicloud.com/intl/en-us/usermanual-ca/ca_01_0003.html.
ak = os.getenv("AccessKeyID")
sk = os.getenv("SecretAccessKey")
# (Optional) If you use a temporary AK and SK pair and a security token to access OBS, obtain them from environment variables.
security_token = os.getenv("SecurityToken")
# Set server to the endpoint corresponding to the bucket. Here uses CN-Hong Kong as an example. Replace it with the one in use.
server = "https://obs.ap-southeast-1.myhuaweicloud.com"

# Create an obsClient instance.
# If you use a temporary AK and SK pair and a security token to access OBS, you must specify security_token when creating an instance.
obsClient = ObsClient(access_key_id=ak, secret_access_key=sk, server=server)
try:
    # Specify custom metadata.
    metadata = {'property1': 'property-value1', 'property2': 'property-value2'}
    # Specify the additional headers of the request for configuring object metadata.
    headers = SetObjectMetadataHeader()
    # (Optional) Specify the MIME type of the object.
    headers.contentType = "Your Content-Type"
    bucketName = "examplebucket"
    objectKey = "objectname"
    # Configure metadata for the object.
    resp = obsClient.setObjectMetadata(bucketName, objectKey, metadata, headers)

    # If status code 2xx is returned, the API is called successfully. Otherwise, the API call fails.
    if resp.status < 300:
        print('Set Object Metadata Succeeded')
        print('requestId:', resp.requestId)
    else:
        print('Set Object Metadata Failed')
        print('requestId:', resp.requestId)
        print('errorCode:', resp.errorCode)
        print('errorMessage:', resp.errorMessage)
except:
    print('Set Object Metadata Failed')
    print(traceback.format_exc())