无法为Flask表单创建带有动态选项的下拉输入

Question

我有以下html文件，我正在其中尝试创建一个多步骤表单，其中某些输入可以下拉。我以前只能使用wtform类中的Flask的SelectField方法来使它工作（如下所示），但是仅此一项现在不起作用。

class InputForm(FlaskForm):

    stack_name = StringField('STACK NAME', validators=[validators.required()])
    deploy_bucket = SelectField('PIPELINE DEPLOYMENT BUCKET', validators=[validators.required()])
    qc = SelectField('QC', choices=[("", "---"), ("","BAM"), ("","VCF")])

@app.route('/', methods=['GET', 'POST'])
def pipeline():

    form = InputForm(request.form)
    form.deploy_bucket.choices = [("", "---")] + [("", bucket["Name"]) for bucket in app.config['S3_CLIENT'].list_buckets()["Buckets"]]

    if request.method == 'POST':
        try:
            STACK_NAME = form.stack_name.data
            DEPLOY_BUCKET = form.deploy_bucket.data
            QC = form.qc.data

我用<select>包围了我希望下拉的输入。我的某些“下拉”输入将具有固定选项，而其他一些将具有动态选项，动态选项将来自app.py中对AWS的api调用。我知道对于固定选项，我只能使用<select>和<option>，但是如何正确地在下面的html文件中为动态选项配置下拉输入？尝试在下面的html文件中。

（注意：deploy_bucket_options正在从我的app.py传递到html文件，并在其中定义为form.resource_cfn_tmpl_deploy_bucket.choices = [("", "---")] + [("", bucket["Name"]) for bucket in app.config['S3_CLIENT'].list_buckets()["Buckets"]])

html / js ：

{% extends 'layout.html' %}

{% block body %}

<form method="POST" id="regForm" action="">
  <h1>Pipeline Input</h1>
  <br>
  <!-- One "tab" for each step in the form: -->
  <div class="tab">Pipeline Infrastructure:
    <p><input placeholder="Stack name..." oninput="this.className = ''" name="stack_name"></p>

    <!-- Here is a dynamic option input, not sure what to do here! -->

    <p><select placeholder="Deploy bucket..." oninput="this.className = ''" name="deploy_bucket">
    {% for option in deploy_bucket_options %}
         <option value="{{ option }}">{{ option }}</option>
    {% endfor %}
    </select>

    <!-- Fixed option input -->

  <select placeholder="QC..." oninput="this.className = ''" name="qc">
    <option value="---">---</option>
    <option value="BAM">BAM</option>
    <option value="VCF">VCF</option>
  </select>
  </div>
</form>

<script>
var currentTab = 0; // Current tab is set to be the first tab (0)
showTab(currentTab); // Display the crurrent tab

function showTab(n) {
  // This function will display the specified tab of the form...
  var x = document.getElementsByClassName("tab");
  x[n].style.display = "block";
  //... and fix the Previous/Next buttons:
  if (n == 0) {
    document.getElementById("prevBtn").style.display = "none";
  } else {
    document.getElementById("prevBtn").style.display = "inline";
  }
  if (n == (x.length - 1)) {
    document.getElementById("nextBtn").innerHTML = "Submit";
  } else {
    document.getElementById("nextBtn").innerHTML = "Next";
  }
  //... and run a function that will display the correct step indicator:
  fixStepIndicator(n)
}

function nextPrev(n) {
  // This function will figure out which tab to display
  var x = document.getElementsByClassName("tab");
  // Exit the function if any field in the current tab is invalid:
  if (n == 1 && !validateForm()) return false;
  // Hide the current tab:
  x[currentTab].style.display = "none";
  // Increase or decrease the current tab by 1:
  currentTab = currentTab + n;
  // if you have reached the end of the form...
  if (currentTab >= x.length) {
    // ... the form gets submitted:
    document.getElementById("regForm").submit();
    return false;
  }
  // Otherwise, display the correct tab:
  showTab(currentTab);
}

function validateForm() {
  // This function deals with validation of the form fields
  var x, y, i, valid = true;
  x = document.getElementsByClassName("tab");
  y = x[currentTab].getElementsByTagName("input");
  // A loop that checks every input field in the current tab:
  for (i = 0; i < y.length; i++) {
    // If a field is empty...
    if (y[i].value == "") {
      // add an "invalid" class to the field:
      y[i].className += " invalid";
      // and set the current valid status to false
      valid = false;
    }
  }
  // If the valid status is true, mark the step as finished and valid:
  if (valid) {
    document.getElementsByClassName("step")[currentTab].className += " finish";
  }
  return valid; // return the valid status
}

function fixStepIndicator(n) {
  // This function removes the "active" class of all steps...
  var i, x = document.getElementsByClassName("step");
  for (i = 0; i < x.length; i++) {
    x[i].className = x[i].className.replace(" active", "");
  }
  //... and adds the "active" class on the current step:
  x[n].className += " active";
}
</script>

{% endblock %}