文件上传-Flask

app.py
```python
app.config['UPLOAD_FOLDER'] = os.getcwd()+"\\upload\\" #定义上传目录
app.config['ALLOWED_EXTENSIONS'] = {'txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif'} #允许的扩展名
```

```python
import os
from werkzeug.utils import secure_filename
from flask import Blueprint, current_app, render_template, request

#其他略

#验证扩展名函数
def allowed_file(filename,ALLOWED_EXTENSIONS):
    return '.' in filename and \
           filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS

@index_index.route('/from')       # /html上传界面
def from_html():
    return render_template('index/from.html')

@index_index.route('/upload',methods=['POST'])       #上传文件
def upload():
    if 'file' not in request.files:
        print('No file part')
        return ''

file = request.files['file']
    if file.filename == '':
        print('No selected file')
        return ''

if file:
        app = current_app._get_current_object()
        if file and allowed_file(file.filename,app.config['ALLOWED_EXTENSIONS']):
		#验证扩展名
            filename = secure_filename(file.filename) #返回安全的文件名
            file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))#上传文件
            return f'File uploaded successfully: {filename}'
        else:
            print("not file type")
            return ''
```

from.html
```html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>File Upload</h1>
    <form method="post" action="/upload" enctype="multipart/form-data">
        <input type="file" name="file" />
        <input type="submit" value="Upload" />
    </form>
</body>
</html>
```