在 Javascript / ES6 中，如何等待 Python 代码在 Jupyter Notebook 中完成执行？

Question

我的代码调用一个 Jupyter Notebook 例程 (kernel.execute)，它接受 Python 命令和回调函数，但该例程不返回 Promise。

是否可以在循环中异步调用 kernel.execute 并等待每个回调？

// these functions print timestamps to the console
var function_1 = {
  iopub: {
    output: parse_json_from_python_and_stash_something_in_object_1();
  }
}

var function_n = {
  iopub: {
    output: parse_json_from_python_and_stash_something_in_object_n();
  }
}

var objects_to_populate = {
  object_1: function_1,
  object_n: function_n
}

handler.on('click', function() {

  $.each(objects_to_populate, function(obj, cb) {
    let arg = '\'' + "Hello from Javascript" + '\'';
    let command = `print(${arg})`;

    // Jupyter Notebook function; calls Python (slow)
    kernel.execute(command, cb);
  }

  ugly_sleep_hack();
  // Do something here after every object has been populated

  print_timestamp_to_console("Finished");
}

Answer 1

你可以使用 es6 async, await：

// emulating async function here
let kernel = {
  execute: (ignore, cb) => setTimeout(cb, 2000)
}

let objects_to_populate = {
  1: () => console.log(1),
  2: () => console.log(2),
  3: () => console.log(3)
};

let execute = function(command, cb) {
  return new Promise(function(resolve, reject) {
    kernel.execute(command, function() {
      cb();
      resolve();
    });
  })
};

let handler = $('#testBtn');

handler.on('click', async function() {
      let executes = [];


      $.each(objects_to_populate, function(obj, cb) {
      
          let arg = '\'' + "Hello from Javascript" + '\'';
          let command = `print(${arg})`;

          // Jupyter Notebook function; calls Python (slow)
          executes.push(execute(command, cb));
        });

        await Promise.all(executes);
        console.log('Something');
        // Do something here after every object has been populated
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button id="testBtn">Test</button>

Answer 2

您还可以编写和使用递归函数。在这里https://mostafa-samir.github.io/async-iterative-patterns-pt1/你可以找到一些解释。类似的东西：

var objects_to_populate = {
  object_1: function_1,
  object_n: function_n
};

const iterateAsync = (collection, keys, i) => {
  if (i < keys.length){
    const obj = collection[keys[i]]; // This is your obj
    const arg = '\'' + "Hello from Javascript" + '\'';
    const command = `print(${arg})`;

    // Jupyter Notebook function; calls Python (slow)
    executes.push(execute(command, (err, res) => {
      if(!err){
        i++;
        iterateAsync(collection, keys, i);
      }
    }));
  }
};

const keys = Object.keys(objects_to_populate); // To create it once
iterateAsync(objects_to_populate, keys, 0);

我不测试它，但你需要类似的东西。