为什么flask_wtf.FlaskForm上传一个文件会给出一个错误,说明该文件没有上传?

如果我打电话 request.files['file'] 我得到了文件对象,但是 form.validate_on_submit() 仍然失败。如果请求中有文件对象,为什么失败?

表单.py

from flask_wtf import FlaskForm
from flask_wtf.file import FileField, FileRequired

class ExcelForm(FlaskForm):
    excel_file = FileField(validators=[
        FileRequired()
    ])

web应用程序.py

from flask import Flask, render_template, redirect, url_for, request
from forms import ExcelForm
import pandas as pd

app = Flask(__name__)
app.config['SECRET_KEY'] = '314159265358'

@app.route('/', methods=['GET', 'POST'])
def upload():
    form = ExcelForm(request.form)

    if request.method == 'POST' and form.validate_on_submit():
        df = pd.read_csv(form.excel_file.data)
        print(df.head())

        return redirect(url_for('hello', name=form.excel_file.data))
    return render_template('upload.html', form=form)

@app.route('/hello/<name>')
def hello(name):
    return 'hello' + name

if __name__ == '__main__':
    app.run(debug=True, host='0.0.0.0', port=5000)

{% extends "layout.html" %}
{% block content %}
<form method = "POST" enctype = "multipart/form-data">
 {{ form.hidden_tag() }}
 <input type = "file" name = "file" />
 <input type = "submit"/>
</form>
{% endblock content %}

我可以进入 localhost:5000/upload 没有问题。我单击浏览按钮,选择我的文件,然后单击提交按钮。

在 webapp.py upload 表单.validate_on_submit() 失败并给我一个错误说 {'excel_file': ['This field is required.']}

我也不想将文件保存在本地以便以后读取。