Simple Flask Streaming Server Example

server.py

from flask import Flask, Response, stream_with_context, request
import time

app = Flask(__name__)


# ================= Basic Streaming =================

@app.route('/hello-world')
def hello_world():
    comments = [
        'Hello',
        'Flask',
        'Stream',
        'Server!',
    ]

    def generate():
        for comment in comments:
            yield '<li>' + comment + '</li>'
            time.sleep(0.5)  # 動作をわかりやすくするために追加

    return Response(generate())


# ================= Jinja2 を使った Streaming =================

def stream_template(template_name, **context):
    app.update_template_context(context)
    t = app.jinja_env.get_template(template_name)
    rv = t.stream(context)
    rv.enable_buffering(5)
    for buffer in rv:
        yield buffer
        time.sleep(0.5)


@app.route('/hello-world-with-template')
def hello_world_with_template():
    comments = ['Count: {}'.format(i) for i in range(20)]
    return Response(stream_template('comment_list.html', comments=comments))


# ================= Streaming with Context =================

@app.route('/stream')
def streamed_response():
    def generate():
        yield 'Hello '
        time.sleep(1)
        yield request.args['name']
        time.sleep(1)
        yield '!'

    return Response(stream_with_context(generate()))


if __name__ == '__main__':
    app.run(host='127.0.0.1', port=5001, debug=True)

templates-comment_list.html

<p>Start!</p>
<ul>
    {% for comment in comments %}
    <li>{{ comment }}</li>
    {% endfor %}
</ul>
<p>Finish!</p>