Three ways to download Flask files

Flask is a popular Python web framework that provides multiple ways to implement file downloads. In this article, we will cover three different approaches so that you can choose the one that best suits your application.

Method 1: Use the send_file function

 send_fileFunctions are one of the most commonly used file download methods in Flask. It allows you to send files from the server to the client without having to read the entire file into memory. The syntax of this function is as follows:

from flask import Flask, send_file

app = Flask(__name__)

@('/download')
def download():
    return send_file('/path/to/file', as_attachment=True)

here,send_fileThe function takes the file name as a parameter and usesas_attachmentThe parameter instructs the browser to download it as an attachment, rather than opening it in the browser.

Method 2: Use the send_from_directory function

 send_from_directoryFunctions andsend_fileThe function is similar, but it is used to send files from a specified directory. The syntax of this function is as follows:

from flask import Flask, send_from_directory

app = Flask(__name__)

@('/download/<filename>')
def download(filename):
    return send_from_directory('/path/to/directory', filename, as_attachment=True)

here,send_from_directoryThe function provides two parameters, the first parameter is the path to the directory and the second parameter is the file name. useas_attachmentParameters can instruct the browser to download it as an attachment.

Method 3: Use the send_file function and the X-Sendfile header

The third method is to usesend_fileFunction and X-Sendfile header. This method requires your web server to support the X-Sendfile header. When Flask sends a response containing the X-Sendfile header, the web server will send the file instead of Flask. This is more efficient than sending files directly with Flask, because Flask does not have to read the entire file or cache it to memory.

In order to use the X-Sendfile header in Flask, you need to setX_SENDFILE_TYPEConfiguration options:

from flask import Flask, send_file

app = Flask(__name__)
['X_SENDFILE_TYPE'] = 'X-Accel-Redirect'

@('/download')
def download():
    return send_file('/path/to/file', as_attachment=True)

here,X_SENDFILE_TYPEThe configuration option specifies the X-Sendfile type to use. In this example, we useX-Accel-Redirect。

In your web server, you need to configure the X-Sendfile header so that it works with Flask. Please refer to your web server documentation for more information.

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