Flask request.files is not in 'file'

I am using Flask Python to integrate a website with a python script. In such a page user should enter an image the this image is passed to the python script to do some processing on it. The problem here is that whenever I enter an image it goes throw

'file' not in request.files

I think problem in POST method but I can't get an answer to solve it. Flask code :

UPLOAD_FOLDER = path
app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER
ALLOWED_EXTENSIONS = ['png', 'jpg', 'jpeg', 'gif']


def allowed_file(filename):
    return '.' in filename and filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS


@app.route('/services')
def services():
    return render_template('services.html')


@app.route('/services', methods=['POST', 'GET'])
def upload_image():
    if 'file' not in request.files:
        flash('No file part')
        return redirect(request.url)

    file = request.files['file']
    if file.filename == '':
        flash('No image selected for uploading')
        return redirect(request.url)
    if file and allowed_file(file.filename):
        filename = secure_filename(file.filename)
        full_path = os.path.join(app.config['UPLOAD_FOLDER'], filename)
        print('save')
        file.save(full_path)

        # print('upload_image filename: ' + filename)
        flash('Image successfully uploaded and displayed')
        return render_template('services.html', filename=filename)
    else:
        flash('Allowed image types are -> png, jpg, jpeg, gif')
        return redirect(request.url)


@app.route('/services/display/<filename>')
def display_image(filename):
    # print('display_image filename: ' + filename)
    return redirect(url_for('static', filename='uploads/' + filename), code=301)

HTML

<form method="post" action="" enctype="multipart/form-data">
    <label for="img" style="margin-bottom: 40px;font-size: 30px">choose image:</label>
    <input type="file" class="form-control col-lg" id="img" autocomplete="off" required name="img">
    <p>
        <input type="submit" value="Submit" name="submit">
    </p>
</form>