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Library that works with Flask & SqlAlchemy to store files in your database and server.

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Library that works with Flask & SqlAlchemy to store files on your server & in your database

Read the docs: Documentation


Please install the latest stable release:

pip install flask-file-upload

Flask File Upload

General Flask config options

(Important: The below configuration variables need to be set before initiating FileUpload)

    # This is the directory that flask-file-upload saves files to. Make sure the UPLOAD_FOLDER is the same as Flasks's static_folder or a child. For example:
    app.config["UPLOAD_FOLDER"] = join(dirname(realpath(__file__)), "static/uploads")

    # Other FLASK config varaibles ...
    app.config["ALLOWED_EXTENSIONS"] = ["jpg", "png", "mov", "mp4", "mpg"]
    app.config["MAX_CONTENT_LENGTH"] = 1000 * 1024 * 1024  # 1000mb
    app.config["SQLALCHEMY_DATABASE_URI"] = "postgresql://localhost:5432/blog_db"


We can either pass the instance to FileUpload(app) or to the init_app(app) method:

app = Flask(__name__, static_folder="static") # IMPORTANT: This is your root directory for serving ALL static content!

db = SQLAlchemy()

file_upload = FileUpload()

# An example using the Flask factory pattern
def create_app():
    # Pass the Flask app instance as the 1st arg &
    # the SQLAlchemy object as the 2nd arg to file_upload.init_app.
    file_upload.init_app(app, db)

# Or we can pass the Flask app instance directly & the Flask-SQLAlchemy instance:
db = SQLAlchemy(app)
# Pass the Flask app instance as the 1st arg &
# the SQLAlchemy object as the 2nd arg to FileUpload
file_upload = FileUpload(app, db)
app: Flask = None

Decorate your SqlAlchemy models

Flask-File-Upload (FFU) setup requires each SqlAlchemy model that wants to use FFU library to be decorated with @file_upload.Model .This will enable FFU to update your database with the extra columns required to store files in your database. Declare your attributes as normal but assign a value of file_upload.Column. This is easy if you are using Flask-SqlAlchemy:

from flask_sqlalchemy import SqlAlchemy

db = SqlAlchemy()

Full example:

from my_app import file_upload

class blogModel(db.Model):
   __tablename__ = "blogs"
   id = db.Column(db.Integer, primary_key=True)

   # Use flask-file-upload's `file_upload.Column()` to associate a file with a SQLAlchemy Model:
   my_placeholder = file_upload.Column()
   my_video = file_upload.Column()

define files to be uploaded:

    # A common scenario could be a video with placeholder image.
    # So first lets grab the files from Flask's request object:
    my_video = request.files["my_video"]
    placeholder_img = request.files["placeholder_img"]

Save files

Now we have the files assigned to variables, we can start using the m with flask-file-upload:

    file_upload.save_files(blog_post, files={
        "my_video": my_video,
        "placeholder_img": placeholder_img,
If you followed the setup above you will see the following structure saved to your app:


Update files

    blog_post = file_upload.update_files(blog_post, files={
        "my_video": new_my_video,
        "placeholder_img": new_placeholder_img,

Delete files

Deleting files from the db & server can be non trivial, especially to keep both in sync. The file_upload.delete_files method can be called with a kwarg of clean_up & then depending of the string value passed it will provide 2 types of clean up functionality:

  • files will clean up files on the server but not update the model
  • model will update the model but not attempt to remove the files from the server. See delete_files Docs for more details
    # Example using a SqlAlchemy model with an appended
    # method that fetches a single `blog`
    blogModel = BlogModel()
    blog_results = blogModel.get_one()

    # We pass the blog & files
    blog = file_upload.delete_files(blog_result, files=["my_video"])

    # If parent kwarg is set to True then the root primary directory & all its contents will be removed.
    # The model will also get cleaned up by default unless set to `False`.
    blog_result = file_upload.delete_files(blog_result, parent=True, files=["my_video"])

    # If the kwarg `commit` is not set or set to True then the updates are persisted.
    # to the session. And therefore the session has been commited.
    blog = file_upload.delete_files(blog_result, files=["my_video"])

    # Example of cleaning up files but not updating the model:
    blog = file_upload.delete_files(blog_result, files=["my_video"], clean_up="files")

Stream a file

    file_upload.stream_file(blog_post, filename="my_video")

File Url paths

    file_upload.get_file_url(blog_post, filename="placeholder_img")

Example for getting file urls from many objects:

    # If blogs_model are many blogs:
    for blog in blog_models:
        blog_image_url = file_upload.get_file_url(blog, filename="blog_image")
        setattr(blog, "blog_image", blog_image_url)

Set file paths to multiple objects - Available in 0.1.0-rc.6 & v0.1.0

The majority of requests will require many entities to be returned & these entities may have SQLAlchemy backrefs with relationships that may also contain Flask-File-Upload (FFU) modified SQLAlchemy models. To make this trivial, this method will set the appropriate filename urls to your SQLAlchemy model objects (if the transaction hasn't completed then add_file_urls_to_models will complete the transaction by default).

The first argument required by this method is models - the SQLAlchemy model(s).

Then pass in the required kwarg filenames which references the parent's FFU Model values - this is the file_upload.Model decorated SQLALchemy model

  • file_upload.Column() method.

Important! Also take note that each attribute set by this method postfixes a _url tag. e.g blog_image becomes blog_image_url

Example for many SQLAlchemy entity objects (or rows in your table)::

    class BlogModel(db.Model):

        blog_image = file_upload.Column()

Now we can use the file_upload.add_file_urls_to_models to add file urls to each SQLAlchemy object. For example::

    blogs = add_file_urls_to_models(blogs, filenames="blog_image")

    # Notice that we can get the file path `blog_image` + `_url`
    assert  blogs[0].blog_image_url == "path/to/blogs/1/blog_image_url.png"

To set filename attributes to a a single or multiple SQLAlchemy parent models with backrefs to multiple child SQLAlchemy models, we can assign to the optional backref kwarg the name of the backref model & a list of the file attributes we set with the FFU Model decorated SQLAlchemy model.

To use backrefs we need to declare a kwarg of backref & pass 2 keys: - name: The name of the backref relation - filenames: The FFU attribute values assigned to the backref model

For example::

    # Parent model
    class BlogModel(db.Model):
        # The backref:
        blog_news = db.relationship("BlogNewsModel", backref="blogs")
        blog_image = file_upload.Column()
        blog_video = file_upload.Column()

    # Model that has a foreign key back up to `BlogModel
    class BlogNewsModel(db.Model):
        # The foreign key assigned to this model:
        blog_id = db.Column(db.Integer, db.ForeignKey("blogs.blog_id"))
        news_image = file_upload.Column()
        news_video = file_upload.Column()

The kwarg backref keys represent the backref model or entity (in the above example this would be the BlogNewsModel which we have named blog_news. Example::

    blogs = add_file_urls_to_models(blogs, filenames=["blog_image, blog_video"],
            "name": "blog_news",`
            "filenames": ["news_image", "news_video],

WARNING: You must not set the relationship kwarg: lazy="dynamic"! If backref is set to "dynamic" then back-referenced entity's filenames will not get set. Example::

    # This will work
    blog_news = db.relationship("BlogNewsModel", backref="blog")

    # this will NOT set filenames on your model class
    blog_news = db.relationship("BlogNewsModel", backref="blog", lazy="dynamic")

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