您可以流式传输响应中的数据，但是不能按照描述的方式动态更新模板。模板在服务器端只渲染一次，然后发送到客户端。您需要使用Javascript读取流式响应并在客户端输出数据。
用于
XMLHttpRequest向要发送数据的端点发出请求。然后定期从流中读取直到完成。
此示例假定一种非常简单的消息格式：一行数据，然后是换行符。当然，只要有一种识别每条消息的方法，解析就可能变得很复杂。例如，您可以返回一个JSON对象并在客户端上对其进行解码。
from time import sleepfrom flask import Flask, render_templatefrom math import sqrtapp = Flask(__name__)@app.route('/')def index(): # render the template (below) that will use Javascript to read the stream return render_template('index.html')@app.route('/stream_sqrt')def stream(): def generate(): for i in range(500): yield '{}n'.format(sqrt(i)) sleep(1) return app.response_class(generate(), mimetype='text/plain')app.run()<p>This is the latest output: <span id="latest"></span></p><p>This is all the output:</p><ul id="output"></ul><script> var latest = document.getElementById('latest'); var output = document.getElementById('output'); var xhr = new XMLHttpRequest(); xhr.open('GET', '{{ url_for('stream') }}'); xhr.send(); var position = 0; function handleNewData() { // the response text include the entire response so far // split the messages, then take the messages that haven't been handled yet // position tracks how many messages have been handled // messages end with a newline, so split will always show one extra empty message at the end var messages = xhr.responseText.split('n'); messages.slice(position, -1).forEach(function(value) { latest.textContent = value; // update the latest value in place // build and append a new item to a list to log all output var item = document.createElement('li'); item.textContent = value; output.appendChild(item); }); position = messages.length - 1; } var timer; timer = setInterval(function() { // check the response for new data handleNewData(); // stop checking once the response has ended if (xhr.readyState == XMLHttpRequest.DONE) { clearInterval(timer); latest.textContent = 'Done'; } }, 1000);</script>
