pip install Markdown==2.3.1

@app.template_filter('md')
def markdown_to_html(txt):
  from markdown import markdown
  return markdown(txt)

@app.route('/', methods=['POST', 'GET'])
def index():
  return render_template('index.html', body='# hello')

{{ body|md|safe }}

def read_md(filename):
  with open(filename) as md_file:
    content = reduce(lambda x, y: x+y, md_file.readline())
  return content.decode('utf-8')

@app.context_processor
def inject_methods():
  return dict(read_md=read_md)

{{ read_md('test.md')|md|safe}}