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Upload file in Flask with Dropzone.js.

Project description


Upload files in Flask application with Dropzone.js.


$ pip install flask-dropzone

Quick Start

Step 1: Initialize the extension:

from flask_dropzone import Dropzone

dropzone = Dropzone(app)

This extension also supports the Flask application factory pattern by allowing you to create a Dropzone object and then separately initialize it for an app:

dropzone = Dropzone()

def create_app(config):
    app = Flask(__name__)
    return app

Step 2: In addition to manage and load resources by yourself (recommend), you can also use this methods to load resources:

{{ dropzone.load_css() }}
{{ dropzone.load_js() }}

There is a dropzone.load() method that was a combination of dropzone.load_css() and dropzone.load_js(), but we recommend not to use this method for page load performance consideration.

You can assign the version of Dropzone.js through version argument, the default value is 5.2.0. And, you can pass css_url and js_url separately to customize resources URL.

Step 3: Creating a Drop Zone with create() and use config() to make the configuration come into effect:

{{ dropzone.create(action='the_url_or_endpoint_which_handle_uploads') }}
{{ dropzone.config() }}

Remember to edit the action to the URL or endpoint which handles the uploads, for example dropzone.create(action=url_for('upload_view')').

Beautify Dropzone

Style it according to your preferences through style() method:

{{ dropzone.load_css() }}
{{'border: 2px dashed #0087F7; margin: 10%; min-height: 400px;') }}


The supported list of config options is shown below:

Name Default Value Info
DROPZONE_SERVE_LOCAL   False       default to retrieve dropzone.js from CDN
DROPZONE_MAX_FILE_SIZE 3 max allowed file size. unit: MB
DROPZONE_INPUT_NAME file the name attr in <input> (i.e. <input type="file" name="file">)
DROPZONE_ALLOWED_FILE_TYPE 'default' see detail below
DROPZONE_MAX_FILES 'null' the max files user can upload once
DROPZONE_DEFAULT_MESSAGE "Drop files here to upload" message displayed on drop area, you can write HTML here (e.g. Drop files here<br>Or<br><button type="button">Click to Upload</button>)
DROPZONE_INVALID_FILE_TYPE "You can't upload files of this type." error message
DROPZONE_FILE_TOO_BIG "File is too big {{filesize}}. Max filesize: {{maxFilesize}}MiB." error message
DROPZONE_SERVER_ERROR "Server error: {{statusCode}}" error message
DROPZONE_BROWSER_UNSUPPORTED "Your browser does not support drag'n'drop file uploads." error message
DROPZONE_MAX_FILE_EXCEED "Your can't upload any more files." error message
DROPZONE_UPLOAD_MULTIPLE False whether to send multiple files in one request.
DROPZONE_PARALLEL_UPLOADS 2 how many uploads will handled in per request when DROPZONE_UPLOAD_MULTIPLE set to True.
DROPZONE_REDIRECT_VIEW None the view to redierct when upload was completed.
DROPZONE_ENABLE_CSRF False enable CSRF protect, see detail below
DROPZONE_TIMEOUT None The timeout to cancel upload request in millisecond, default to 30000 (30 second). Set a large number if you need to upload large file.

You can use these file type:

allowed_file_type = {
    'default': 'image/*, audio/*, video/*, text/*, application/*',
    'image': 'image/*',
    'audio': 'audio/*',
    'video': 'video/*',
    'text': 'text/*',
    'app': 'application/*'

Just set DROPZONE_ALLOWED_FILE_TYPE to one of default, image, audio, video, text, app, for example:

app.config['DROPZONE_ALLOWED_FILE_TYPE'] = 'image'

If you want to set the allowed file type by yourself, you need to set DROPZONE_ALLOWED_FILE_CUSTOM to True, then add mime type or file extensions to DROPZONE_ALLOWED_FILE_TYPE, such as:

app.config['DROPZONE_ALLOWED_FILE_TYPE'] = 'image/*, .pdf, .txt'

Consult the dropzone.js documentation for details on these options.

Save uploads with Flask

import os

from flask import Flask, request
from flask_dropzone import Dropzone

app = Flask(__name__)

dropzone = Dropzone(app)

@app.route('/uploads', methods=['GET', 'POST'])
def upload():

    if request.method == 'POST':
        f = request.files.get('file')'the/path/to/save', f.filename))

    return 'upload template'

See examples/basic for more detail.

Parallel Uploads

If you set DROPZONE_UPLOAD_MULTIPLE as True, then you need to save multiple uploads in single request.

However, you can't get a list of file with request.files.getlist('file'). When you enable parallel upload, Dropzone.js will append a index number after each files, for example: file[2], file[1], file[0]. So, you have to save files like this:

    for key, f in request.files.iteritems():
        if key.startswith('file'):
  'the/path/to/save', f.filename)) 

Here is the full example:

app.config['DROPZONE_UPLOAD_MULTIPLE'] = True  # enable parallel upload
app.config['DROPZONE_PARALLEL_UPLOADS'] = 3  # handle 3 file per request

@app.route('/upload', methods=['GET', 'POST'])
def upload():
    if request.method == 'POST':
        for key, f in request.files.iteritems():  # use request.files.items() in Python3
            if key.startswith('file'):
      'the/path/to/save', f.filename))

    return 'upload template'

See examples/parallel-upload for more detail.

CSRF Protect

The CSRF Protect feature was provided by Flask-WTF's CSRFProtect extension, so you have to install Flask-WTF first:

$ pip install flask-wtf

Then initialize the CSRFProtect:

from flask_wtf.csrf import CSRFProtect

app = Flask(__name__)

# the secret key used to generate CSRF token
app.config['SECRET_KEY'] = 'dev key' 
# enable CSRF protection
app.config['DROPZONE_ENABLE_CSRF'] = True  

csrf = CSRFProtect(app)

Make sure to set the secret key and set DROPZONE_ENABLE_CSRF to True. Now all the upload request will be protected!

We prefer to handle the CSRF error manually, because the error response's body will be displayed as tooltip below the file thumbnail.

from flask_wtf.csrf import CSRFProtect, CSRFError

# handle CSRF error
def csrf_error(e):
    return e.description, 400

Here I use the e.description as error message, it's provided by CSRFProtect, one of The CSRF token is missing and The CSRF token is invaild.

Try the demo application in examples/csrf and see CSRFProtect's documentation for more details.

Server Side Validation

Although Dropzone.js can handle client side validation for uploads, but you still need to setup server side validation for security conern. Just do what you normally do (extension check, size check etc.), the only thing you should remember is to return plain text error message as response body when something was wrong. Fox example, if we only want user to upload file with .png extension, we can do the validation like this:

@app.route('/', methods=['POST', 'GET'])
def upload():
    if request.method == 'POST':
        f = request.files.get('file')
        if f.filename.split('.')[1] != 'png':
            return 'PNG only!', 400  # return the error message, with a proper 4XX code'the/path/to/save', f.filename))
    return render_template('index.html')

The error message will be displayed when you hover the thumbnail for upload file:

error message


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