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Downloading Objects
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Last updated: 2024-02-04 16:24:43
Downloading Objects
Last updated: 2024-02-04 16:24:43
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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.cloud.tencent.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.cloud.tencent.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.cloud.tencent.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.cloud.tencent.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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