controller

@core.route('/create', methods=['GET', 'POST'])
@login_required
def create():
    form = BlogForm()
    if request.method == 'POST' and form.validate_on_submit():
        f = form.image.data
        file_path = save_file(f)
        blog = Blog(title=form.title.data, description=form.description.data, image=file_path, user_id=current_user.id)
        db.session.add(blog)
        db.session.commit()
        flash('Melumat elave edildi')
        return redirect('/')
    context = {
        'form': form
    }
    return render_template('core/create.html', **context)

init

from flask import Flask, session, send_from_directory

BASE_DIRS = os.path.dirname(os.path.abspath(__file__)) 
UPLOADED_FILES_DIR = os.path.join(BASE_DIRS, 'media')
app.config['UPLOAD_FOLDER'] = UPLOADED_FILES_DIR

if not os.path.isdir(UPLOADED_FILES_DIR):
    os.mkdir(UPLOADED_FILES_DIR)

@app.route('/uploads/<filename>')
def uploaded_file(filename):
    return send_from_directory(UPLOADED_FILES_DIR,
                               filename)

utils.py

from flask import url_for
from blog import UPLOADED_FILES_DIR, os
from werkzeug.utils import secure_filename
from datetime import datetime


def save_file(f):
    filename = secure_filename(f.filename)
    filename = f'{datetime.now()}_{filename}'
    file_dir = os.path.join(
        UPLOADED_FILES_DIR, filename
    )
    f.save(file_dir)
    file_path = url_for('uploaded_file', filename=filename) # '/uploads/<filename>'
    return file_path