python-boto3/docs/source/guide/s3-example-download-file.rst

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#################
Downloading files
#################

The methods provided by the AWS SDK for Python to download files are similar 
to those provided to upload files.

The ``download_file`` method accepts the names of the bucket and object to 
download and the filename to save the file to.

.. code-block:: python

    import boto3

    s3 = boto3.client('s3')
    s3.download_file('BUCKET_NAME', 'OBJECT_NAME', 'FILE_NAME')


The ``download_fileobj`` method accepts a writeable file-like object. The file 
object must be opened in binary mode, not text mode.

.. code-block:: python

    s3 = boto3.client('s3')
    with open('FILE_NAME', 'wb') as f:
        s3.download_fileobj('BUCKET_NAME', 'OBJECT_NAME', f)


Like their upload cousins, the download methods are provided by the 
S3 ``Client``, ``Bucket``, and ``Object`` classes, and each class provides 
identical functionality. Use whichever class is convenient.

Also like the upload methods, the download methods support the optional 
``ExtraArgs`` and ``Callback`` parameters.

The list of valid ``ExtraArgs`` settings for the download methods is 
specified in the ``ALLOWED_DOWNLOAD_ARGS`` attribute of the ``S3Transfer`` 
object at :py:attr:`boto3.s3.transfer.S3Transfer.ALLOWED_DOWNLOAD_ARGS`.

The download method's ``Callback`` parameter is used for the same purpose 
as the upload method's. The upload and download methods can both invoke the 
same ``Callback`` class.