Flask中使用send_file实现文件下载报错求助

问题概述 #

开发Flask应用时，用户无法下载与主程序同目录的CSV文件以及static目录下的图片，功能失效，以下是相关代码、目录结构及报错信息。

原代码展示 #

Python代码 #

app = Flask(__name__)

@app.route('/', methods= ['POST', 'GET'])
def result():
    if request.method == 'GET':
        return render_template('result.html')
    elif request.method == 'POST':
             
            if request.form['submit_button'] == 'Download CSV':
                return send_file('name.csv', as_attachment=True, download_name='name.csv')
                

            elif request.form['submit_button'] == 'Download plot':
                return Flask.send_static_file('static/plot.png', as_attachment=True, download_name='plot.png')
                              

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

HTML代码 #

<div class = 'wrap'>
     
 
    <form method="POST">

        <input type="submit" name="submit_button" value="Download CSV">
        <input type="submit" name="submit_button" value="Download plot">

    </form>
</div>

目录结构 #

报错信息 #

故障原因与修复方案 #

1. 缺失必要导入语句 #

原代码未导入request、send_file等核心模块，直接运行会触发NameError。需在代码开头补充：

from flask import Flask, render_template, request, send_file
import os

2. CSV文件路径不可靠 #

直接使用相对路径'name.csv'可能因运行时工作目录不一致导致文件找不到，改用应用根目录拼接绝对路径：

csv_path = os.path.join(app.root_path, 'name.csv')
return send_file(csv_path, as_attachment=True, download_name='name.csv')

3. 静态文件下载方法错误 #

Flask.send_static_file调用方式错误，且参数不应包含static/前缀（send_static_file默认从static目录查找）。推荐用send_file配合绝对路径读取图片，更直观可靠：

plot_path = os.path.join(app.root_path, 'static', 'plot.png')
return send_file(plot_path, as_attachment=True, download_name='plot.png')

修复后的完整Python代码 #

from flask import Flask, render_template, request, send_file
import os

app = Flask(__name__)

@app.route('/', methods= ['POST', 'GET'])
def result():
    if request.method == 'GET':
        return render_template('result.html')
    elif request.method == 'POST':
        if request.form['submit_button'] == 'Download CSV':
            csv_path = os.path.join(app.root_path, 'name.csv')
            return send_file(csv_path, as_attachment=True, download_name='name.csv')
        elif request.form['submit_button'] == 'Download plot':
            plot_path = os.path.join(app.root_path, 'static', 'plot.png')
            return send_file(plot_path, as_attachment=True, download_name='plot.png')

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

内容的提问来源于stack exchange，提问作者Juan Ignacio Ochotorena