Django :下拉菜单，仅显示未配置的值

# forms.py
from django import forms

class MyForm(forms.Form):
    OPTIONS = [
        ('value1', 'Option 1'),
        ('value2', 'Option 2'),
        ('value3', 'Option 3'),
        ('value4', 'Option 4'),
        # 添加其他选项...
    ]

    dropdown = forms.ChoiceField(choices=OPTIONS)

# views.py
from django.shortcuts import render
from .forms import MyForm

def my_view(request):
    form = MyForm()
    return render(request, 'my_template.html', {'form': form})

# my_template.html
<form method="POST">
  {% csrf_token %}
  <select>
    {% for option in form.dropdown.field.choices %}
      {% if not option.0 in form.initial.dropdown %}
        <option value="{{ option.0 }}">{{ option.1 }}</option>
      {% endif %}
    {% endfor %}
  </select>
  <button type="submit">Submit</button>
</form>