BUG FIX

[liujiyaoFDU]

When I ran app.py, there went errors:

NameError: name 'Flask' is not defined
NameError: name 'request' is not defined
NameError: name 'render_template' is not defined
NameError: name 'send_file' is not defined

This bug can be fixed by adding this line in app.py(line 5)

from flask import Flask, request, render_template, send_file

[chenluda]

感谢 @Jy-stdio 的提醒，已修改对应代码。