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Downloading Objects

Last updated: 2024-02-04 16:24:43

    Overview

    This document provides an overview of APIs and SDK code samples for simple operations, multipart operations, and other object operations.
    API
    Operation
    Description
    Downloading an object
    Downloads an object to local

    Advanced APIs (Recommended)

    Downloading an object (checkpoint restart)

    Feature description

    This advanced download API can determine whether to download a file in whole or in parts based on the file size. It downloads files smaller than or equal to 20 MB in whole and files larger than 20 MB in parts. It also supports automatic checkpoint restart for suspended multipart downloads.

    Method prototype

    download_file(Bucket, Key, DestFilePath, PartSize=20, MAXThread=5, EnableCRC=False, **Kwargs)

    Sample request

    # -*- coding=utf-8
    from qcloud_cos import CosConfig
    from qcloud_cos import CosS3Client
    from qcloud_cos.cos_exception import CosClientError, CosServiceError
    import sys
    import os
    import logging
    
    # In most cases, set the log level to INFO. If you need to debug, you can set it to DEBUG and the SDK will print information about the communication with the server.
    logging.basicConfig(level=logging.INFO, stream=sys.stdout)
    
    # 1. Set user attributes such as secret_id, secret_key, and region. Appid has been removed from CosConfig and thus needs to be specified in Bucket, which is formatted as BucketName-Appid.
    secret_id = os.environ['COS_SECRET_ID'] # User `SecretId`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    secret_key = os.environ['COS_SECRET_KEY'] # User `SecretKey`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    region = 'ap-beijing' # Replace it with the actual region, which can be viewed in the console at https://console.tencentcloud.com/cos5/bucket.
    # For the list of regions supported by COS, visit https://www.tencentcloud.com/document/product/436/6224.
    token = None # Token is required for temporary keys but not permanent keys. For more information about how to generate and use a temporary key, visit https://www.tencentcloud.com/document/product/436/14048.
    scheme = 'https' # Specify whether to use HTTP or HTTPS protocol to access COS. This field is optional and is `https` by default.
    
    config = CosConfig(Region=region, SecretId=secret_id, SecretKey=secret_key, Token=token, Scheme=scheme)
    client = CosS3Client(config)
    
    # Use the advanced API to download once without retry. In this case, the checkpoint restart feature is not used.
    response = client.download_file(
    Bucket='examplebucket-1250000000',
    Key='exampleobject',
    DestFilePath='local.txt'
    )
    
    # Use the advanced API for checkpoint restart, and the successfully uploaded parts will not be downloaded again during retries (10 retries here).
    for i in range(0, 10):
    try:
    response = client.download_file(
    Bucket='examplebucket-1250000000',
    Key='exampleobject',
    DestFilePath='local.txt')
    break
    except CosClientError or CosServiceError as e:
    print(e)

    Sample request with all parameters

    def upload_percentage(consumed_bytes, total_bytes):
    """Callback function that calculates the upload progress (in percentage)
    
    :param consumed_bytes: uploaded data amount
    :param total_bytes: total data amount
    """
    if total_bytes:
    rate = int(100 * (float(consumed_bytes) / float(total_bytes)))
    print('\\r{0}% '.format(rate))
    sys.stdout.flush()
    
    response = client.download_file(
    Bucket='examplebucket-1250000000',
    Key='exampleobject',
    DestFilePath='local.txt',
    PartSize=1,
    MAXThread=5,
    EnableCRC=True,
    TrafficLimit='1048576'
    IfMatch='"9a4802d5c99dafe1c04da0a8e7e166bf"',
    IfModifiedSince='Wed, 28 Oct 2014 20:30:00 GMT',
    IfNoneMatch='"9a4802d5c99dafe1c04da0a8e7e166bf"',
    IfUnmodifiedSince='Wed, 28 Oct 2014 20:30:00 GMT',
    ResponseCacheControl='string',
    ResponseContentDisposition='string',
    ResponseContentEncoding='string',
    ResponseContentLanguage='string',
    ResponseContentType='string',
    ResponseExpires='string',
    VersionId='string',
    progress_callback=upload_percentage
    )

    Parameter description

    Parameter
    Description
    Type
    Required
    Bucket
    Bucket name in the format of BucketName-APPID
    String
    Yes
    Key
    Object key, which uniquely identifies an object in a bucket. For example, if an object’s access endpoint is examplebucket-1250000000.cos.ap-guangzhou.myqcloud.com/doc/pic.jpg, its key is doc/pic.jpg.
    String
    Yes
    DestFilePath
    Local path to save the downloaded file
    String
    Yes
    PartSize
    Part size for multipart download. Default value: 20 MB
    Int
    No
    MAXThread
    Maximum number of concurrent threads for a multipart download. Default value: 5
    Int
    No
    EnableCRC
    Whether to enable CRC for local and remote files. Default: False
    Bool
    No
    TrafficLimit
    Bandwidth limit in bit/s for a single request (or a single thread for the advanced download API). Value range: 819200 - 838860800, i.e., 100 KB/s - 100 MB/s
    String
    No
    IfMatch
    ETag that needs to be matched. The object is downloaded only if its ETag matches the value.
    String
    No
    IfModifiedSince
    Required modification time. The object is downloaded only if it has been modified after the specified time.
    String
    No
    IfNoneMatch
    ETag that cannot be matched. The object is downloaded only if its ETag does not match the value.
    String
    No
    IfUnmodifiedSince
    Required unmodified time. The object is downloaded only if it has not been modified since the specified time.
    String
    No
    ResponseCacheControl
    Cache-Control of the response header
    String
    No
    ResponseContentDisposition
    Content-Disposition of the response header
    String
    No
    ResponseContentEncoding
    Content-Encoding of the response header
    String
    No
    ResponseContentLanguage
    Content-Language of the response header
    String
    No
    ResponseContentType
    Content-Type of the response header
    String
    No
    ResponseExpires
    Expires of the response header
    String
    No
    VersionId
    Version ID of the object to download
    String
    No
    progress_callback
    Callback function for the upload progress. You can customize this function to query the upload progress.
    Func
    No

    Response description

    None

    Batch downloading files (downloading a COS directory)

    Feature description

    The following example shows how to use the SDK’s basic APIs to download a COS directory to local storage.

    Sample request

    # -*- coding=utf-8
    import os
    import logging
    import sys
    import json
    import os
    
    from qcloud_cos import CosConfig, CosServiceError
    from qcloud_cos import CosS3Client
    from qcloud_cos.cos_threadpool import SimpleThreadPool
    
    # In most cases, set the log level to INFO. If you need to debug, you can set it to DEBUG and the SDK will print information about the communication with the server.
    logging.basicConfig(level=logging.INFO, stream=sys.stdout)
    
    # 1. Set user attributes such as secret_id, secret_key, and region. Appid has been removed from CosConfig and thus needs to be specified in Bucket, which is formatted as BucketName-Appid.
    secret_id = os.environ['COS_SECRET_ID'] # User `SecretId`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    secret_key = os.environ['COS_SECRET_KEY'] # User `SecretKey`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    region = 'ap-beijing' # Replace it with the actual region, which can be viewed in the console at https://console.tencentcloud.com/cos5/bucket.
    # For the list of regions supported by COS, visit https://www.tencentcloud.com/document/product/436/6224.
    token = None # Token is required for temporary keys but not permanent keys. For more information about how to generate and use a temporary key, visit https://www.tencentcloud.com/document/product/436/14048.
    scheme = 'https' # Specify whether to use HTTP or HTTPS protocol to access COS. This field is optional and is `https` by default.
    
    config = CosConfig(Region=region, SecretId=secret_id, SecretKey=secret_key, Token=token, Scheme=scheme) # Obtain the object to configure
    client = CosS3Client(config)
    
    # Bucket information
    test_bucket = 'examplebucket-1250000000'
    start_prefix = 'data/'
    # COS uses slashes (/) to indicate folders.
    # The delimiter parameter is left empty by default, which lists all subdirectories under the directories to achieve the recursive effect of a local folder.
    # If the delimiter parameter is set to "/", you need to handle subdirectories recursively in the SDK.
    delimiter = ''
    
    
    # List and return information about all subdirectories under the current directory.
    def listCurrentDir(prefix):
    file_infos = []
    sub_dirs = []
    marker = ""
    count = 1
    while True:
    response = client.list_objects(test_bucket, prefix, delimiter, marker)
    # Debug the output.
    # json_object = json.dumps(response, indent=4)
    # print(count, " =======================================")
    # print(json_object)
    count += 1
    
    if "CommonPrefixes" in response:
    common_prefixes = response.get("CommonPrefixes")
    sub_dirs.extend(common_prefixes)
    
    if "Contents" in response:
    contents = response.get("Contents")
    file_infos.extend(contents)
    
    if "NextMarker" in response.keys():
    marker = response["NextMarker"]
    else:
    break
    
    print("=======================================================")
    
    # If the delimiter parameter is set to "/", you need to handle subdirectories recursively.
    # sorted(sub_dirs, key=lambda sub_dir: sub_dir["Prefix"])
    # for sub_dir in sub_dirs:
    # print(sub_dir)
    # sub_dir_files = listCurrentDir(sub_dir["Prefix"])
    # file_infos.extend(sub_dir_files)
    
    print("=======================================================")
    
    sorted(file_infos, key=lambda file_info: file_info["Key"])
    for file in file_infos:
    print(file)
    return file_infos
    
    
    # Download files to a local directory. Local files with the same name (if any) will be overwritten.
    # If the directory structure does not exist, a directory structure will be created according to that in COS.
    def downLoadFiles(file_infos):
    localDir = "./download/"
    
    pool = SimpleThreadPool()
    for file in file_infos:
    # Download files to local.
    file_cos_key = file["Key"]
    localName = localDir + file_cos_key
    
    # If the local directory does not exist, create it recursively.
    if not os.path.exists(os.path.dirname(localName)):
    os.makedirs(os.path.dirname(localName))
    
    # skip dir, no need to download it
    if str(localName).endswith("/"):
    continue
    
    # Download files
    # Use a thread pool.
    pool.add_task(client.download_file, test_bucket, file_cos_key, localName)
    
    # Download in whole
    # response = client.get_object(
    # Bucket=test_bucket,
    # Key=file_cos_key,
    # )
    # response['Body'].get_stream_to_file(localName)
    
    pool.wait_completion()
    return None
    
    
    # Encapsulate the feature. Download a COS directory to local.
    def downLoadDirFromCos(prefix):
    global file_infos
    
    try:
    file_infos = listCurrentDir(prefix)
    
    except CosServiceError as e:
    print(e.get_origin_msg())
    print(e.get_digest_msg())
    print(e.get_status_code())
    print(e.get_error_code())
    print(e.get_error_msg())
    print(e.get_resource_location())
    print(e.get_trace_id())
    print(e.get_request_id())
    
    downLoadFiles(file_infos)
    return None
    
    
    if __name__ == "__main__":
    downLoadDirFromCos(start_prefix)

    Simple Operations

    Downloading an object

    Feature description

    This API (GET Object) is used to download an object.

    Method prototype

    get_object(Bucket, Key, **kwargs)

    Sample 1: downloading an object

    # -*- coding=utf-8
    from qcloud_cos import CosConfig
    from qcloud_cos import CosS3Client
    import sys
    import os
    import logging
    
    # In most cases, set the log level to INFO. If you need to debug, you can set it to DEBUG and the SDK will print information about the communication with the server.
    logging.basicConfig(level=logging.INFO, stream=sys.stdout)
    
    # 1. Set user attributes such as secret_id, secret_key, and region. Appid has been removed from CosConfig and thus needs to be specified in Bucket, which is formatted as BucketName-Appid.
    secret_id = os.environ['COS_SECRET_ID'] # User `SecretId`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    secret_key = os.environ['COS_SECRET_KEY'] # User `SecretKey`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    region = 'ap-beijing' # Replace it with the actual region, which can be viewed in the console at https://console.tencentcloud.com/cos5/bucket.
    # For the list of regions supported by COS, visit https://www.tencentcloud.com/document/product/436/6224.
    token = None # Token is required for temporary keys but not permanent keys. For more information about how to generate and use a temporary key, visit https://www.tencentcloud.com/document/product/436/14048.
    scheme = 'https' # Specify whether to use HTTP or HTTPS protocol to access COS. This field is optional and is `https` by default.
    
    config = CosConfig(Region=region, SecretId=secret_id, SecretKey=secret_key, Token=token, Scheme=scheme)
    client = CosS3Client(config)
    
    response = client.get_object(
    Bucket='examplebucket-1250000000',
    Key='exampleobject'
    )
    response['Body'].get_stream_to_file('exampleobject')

    Sample 2: partially downloading an object

    # -*- coding=utf-8
    from qcloud_cos import CosConfig
    from qcloud_cos import CosS3Client
    import sys
    import os
    import logging
    
    # In most cases, set the log level to INFO. If you need to debug, you can set it to DEBUG and the SDK will print information about the communication with the server.
    logging.basicConfig(level=logging.INFO, stream=sys.stdout)
    
    # 1. Set user attributes such as secret_id, secret_key, and region. Appid has been removed from CosConfig and thus needs to be specified in Bucket, which is formatted as BucketName-Appid.
    secret_id = os.environ['COS_SECRET_ID'] # User `SecretId`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    secret_key = os.environ['COS_SECRET_KEY'] # User `SecretKey`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/32675.
    region = 'ap-beijing' # Replace it with the actual region, which can be viewed in the console at https://console.tencentcloud.com/cos5/bucket.
    # For the list of regions supported by COS, see https://www.tencentcloud.com/document/product/436/6224
    token = None # Token is required for temporary keys but not permanent keys. For more information about how to generate and use a temporary key, visit https://www.tencentcloud.com/document/product/436/14048.
    scheme = 'https' # Specify whether to use HTTP or HTTPS protocol to access COS. This field is optional and is `https` by default.
    
    config = CosConfig(Region=region, SecretId=secret_id, SecretKey=secret_key, Token=token, Scheme=scheme)
    client = CosS3Client(config)
    
    response = client.get_object(
    Bucket='examplebucket-1250000000',
    Key='exampleobject',
    Range='bytes=0-100'
    )
    response['Body'].get_stream_to_file('exampleobject')

    Sample request with all parameters

    response = client.get_object(
    Bucket='examplebucket-1250000000',
    Key='exampleobject',
    Range='string',
    IfMatch='"9a4802d5c99dafe1c04da0a8e7e166bf"',
    IfModifiedSince='Wed, 28 Oct 2014 20:30:00 GMT',
    IfNoneMatch='"9a4802d5c99dafe1c04da0a8e7e166bf"',
    IfUnmodifiedSince='Wed, 28 Oct 2014 20:30:00 GMT',
    ResponseCacheControl='string',
    ResponseContentDisposition='string',
    ResponseContentEncoding='string',
    ResponseContentLanguage='string',
    ResponseContentType='string',
    ResponseExpires='string',
    VersionId='string',
    TrafficLimit='819200'
    )

    Parameter description

    Parameter
    Description
    Type
    Required
    Bucket
    Bucket name in the format of BucketName-APPID
    String
    Yes
    Key
    Object key, which uniquely identifies an object in a bucket. For example, if an object’s access endpoint is examplebucket-1250000000.cos.ap-guangzhou.myqcloud.com/doc/pic.jpg, its key is doc/pic.jpg.
    String
    Yes
    Range
    Byte range of the object to download. Format: bytes=first-last
    String
    No
    IfMatch
    ETag that needs to be matched. The object is downloaded only if its ETag matches the value.
    String
    No
    IfModifiedSince
    Required modification time. The object is downloaded only if it has been modified after the specified time.
    String
    No
    IfNoneMatch
    ETag that cannot be matched. The object is downloaded only if its ETag does not match the value.
    String
    No
    IfUnmodifiedSince
    Required unmodified time. The object is downloaded only if it has not been modified since the specified time.
    String
    No
    ResponseCacheControl
    Cache-Control of the response header
    String
    No
    ResponseContentDisposition
    Content-Disposition of the response header
    String
    No
    ResponseContentEncoding
    Content-Encoding of the response header
    String
    No
    ResponseContentLanguage
    Content-Language of the response header
    String
    No
    ResponseContentType
    Content-Type of the response header
    String
    No
    ResponseExpires
    Expires of the response header
    String
    No
    VersionId
    Version ID of the object to download
    String
    No
    TrafficLimit
    Bandwidth limit in bit/s for a single request (or a single thread for the advanced download API). Value range: 819200 - 838860800, i.e., 100 KB/s - 100 MB/s
    String
    No

    Response description

    The response contains the content and metadata of the downloaded object in dict format:
    {
    'Body': StreamBody(),
    'ETag': '"9a4802d5c99dafe1c04da0a8e7e166bf"',
    'Last-Modified': 'Wed, 28 Oct 2014 20:30:00 GMT',
    'Accept-Ranges': 'bytes',
    'Content-Range': 'bytes 0-16086/16087',
    'Cache-Control': 'max-age=1000000',
    'Content-Type': 'application/octet-stream',
    'Content-Disposition': 'attachment; filename="filename.jpg"',
    'Content-Encoding': 'gzip',
    'Content-Language': 'zh-cn',
    'Content-Length': '16807',
    'Expires': 'Wed, 28 Oct 2019 20:30:00 GMT',
    'x-cos-meta-test': 'test',
    'x-cos-version-id': 'MTg0NDUxODMzMTMwMDM2Njc1ODA',
    'x-cos-request-id': 'NTg3NzQ3ZmVfYmRjMzVfMzE5N182NzczMQ=='
    }
    Parameter
    Description
    Type
    Body
    Content of the downloaded object. You can use the `get_raw_stream()` method to get a file stream and the `get_stream_to_file(local_file_path)` method to download the object’s content to a specified local file.
    StreamBody
    ETag
    MD5 checksum of the object
    String
    Last-Modified
    Time when the object was last modified
    String
    Accept-Ranges
    Range unit. HTTP standard header
    String
    Content-Range
    Content range. HTTP standard header
    String
    Cache-Control
    Cache policy. HTTP standard header
    String
    Content-Type
    Content type. HTTP standard header
    String
    Content-Disposition
    Filename. HTTP standard header
    String
    Content-Encoding
    Encoding format. HTTP standard header
    String
    Content-Language
    Language type. HTTP standard header
    String
    Content-Length
    Object size
    String
    Expires
    Cache expiration time. HTTP standard header
    String
    x-cos-meta-*
    User-defined object metadata. It must start with `x-cos-meta`; otherwise, it will be ignored.
    String
    x-cos-version-id
    Version ID of the object if versioning is enabled
    String
    
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