Upload with Flask, Flask-WTF, WTForms and WTForms-Alchemy

controllers.achievements.py

import os

from app                    import app
from app.database           import db_session
from app.models.achievement import Achievement
from app.forms.achievement  import AchievementForm

from flask    import Blueprint, render_template, abort, request, redirect, flash, url_for
from werkzeug import secure_filename

achievements = Blueprint('achievements', __name__, template_folder = 'templates/achievements')

@achievements.route('/new')
def new():
    form = AchievementForm()

    return render_template('achievements/new.html', form=form)


@achievements.route('/create', methods = ['POST']) 
def create():
    model = Achievement()
    form  = AchievementForm()

    if form.validate_on_submit():
        if form.label_path.data:
            image_data = request.files[form.label_path.name].read()
            # after validation field data equal the secure filename
            open(os.path.join(app.config['UPLOAD_PATH'], form.label_path.data), 'w').write(image_data)

        form.populate_obj(model)
        db_session.add(model)
        db_session.commit()

        flash("Achievement created")

        return redirect(url_for('achievements.new'))

    return render_template('achievements/new.html', form=form)

forms.__init__.py

__all__ = ["user", "achievement"]

from flask.ext.wtf import Form
from wtforms_alchemy import model_form_factory

# Using WTForms-Alchemy with Flask-WTF (http://wtforms-alchemy.readthedocs.org/en/latest/advanced.html#using-wtforms-alchemy-with-flask-wtf) to include all good features of Flask-WTF https://flask-wtf.readthedocs.org/en/latest/#features
ModelForm = model_form_factory(Form)

forms.achievement.py

from app.forms              import ModelForm
from app.models.achievement import Achievement

from flask_wtf.file import FileField, FileAllowed, FileRequired
from werkzeug       import secure_filename


class AchievementForm(ModelForm):
    class Meta:
        model  = Achievement
        exclude = ['slug']

    label_path = FileField(None, [
        FileRequired(),
        FileAllowed(['svg'], 'SVG image only!')
    ])

    # change value of field to name of file
    def validate_label_path(form, field):
        if field.data:
            field.data = secure_filename(field.data.filename)

models.achievement.py

from sqlalchemy import Column, Integer, Boolean, String, Text, ForeignKey
from sqlalchemy.orm import relationship
from app.database import Base
from sqlalchemy_sluggable import Sluggable

from app.models.user import User

class Achievement(Base, Sluggable):
    __tablename__ = 'achievements'
    __sluggable__ = {
        'populate_from': 'name',
        'always_update': True
    }

    id               = Column(Integer, primary_key = True, nullable = False)
    user_id          = Column(Integer, ForeignKey('users.id'))
    name             = Column(String(255), unique = True, nullable = False)
    description      = Column(Text)
    label_path       = Column(String(255), nullable = False)

    user = relationship("User")

    def __init__(self, name = None):
        self.name = name

    def __repr__(self):
        return '<Achievement %r>' % (self.name)

templates.achievements.new.html

{% from "helpers/_form.html" import render_field %}

<h1>New</h1>

<form method="POST" action="{{ url_for('achievements.create') }}" enctype="multipart/form-data">
    <dl>
        {{ form.hidden_tag() }}
        {{ render_field(form.name) }}
        {{ render_field(form.description) }}
        {{ render_field(form.label_path) }}
        {{ render_field(form.label_color) }}
        {{ render_field(form.label_background) }}
    </dl>
    <p>
        <input type="submit" value="create">
    </p>
</form>