Flask项目mypred变量引用前未赋值UnboundLocalError问题求助

• 你的路由同时处理GET、POST两种请求，用户首次访问页面触发GET请求时，if request.method == "POST" 分支不会执行，mypred变量未定义就直接传给模板，就会触发NameError，这也是你删掉name=mypred后程序就正常的核心原因
• 多余的global pred全局变量声明没有必要，反而会引发多请求场景下的变量污染问题
• 你把模型加载逻辑写在预测函数里，每次请求都会重新读取一次model.pkl文件，性能极低，频繁请求还可能触发文件IO异常

!pip install flask-ngrok

from flask import Flask, render_template, request
from flask_ngrok import run_with_ngrok
import pickle

app = Flask(__name__, template_folder="templates")
run_with_ngrok(app)   

# 全局仅加载一次模型，避免每次请求重复读文件
model = pickle.load(open('model.pkl', 'rb'))
def cloud_prediction(time):
  return float(model.forecast(time)[0][time-1])

@app.route("/", methods= ["GET", "POST"])
def final():
  # 给预测结果设置默认空值，适配GET请求场景
  mypred = ""
  if request.method =="POST":
    time = int(request.form["time"])
    mypred = cloud_prediction(time)
    print(mypred)
  return render_template("index.html", name= mypred)


if __name__=="__main__":
  app.run()

你当前的HTML存在两处不影响核心功能的语法问题，可按需修复：

• 重复定义了<body>标签，可删除第二个<body bgcolor='black' text='white'>，把属性合并到第一个body标签上
• <h1>标签未闭合，末尾修改为</h1>
• <font>标签未闭合，补充</font>闭合标签
  修复后的参考HTML：

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>WeatherNexus Inc.</title>
  <meta name="description" content="A fortune teller for cloud activity.">
  <meta name="author" content="Jesus_Lopez">
  <meta property="og:title" content="WeatherNexus Inc.">
  <meta property="og:type" content="website">
  <meta property="og:description" content="A fortune teller for cloud activity.">
</head>
<body bgcolor='black' text='white'>
  <h1>WeatherNexus Inc.</h1>
  <p>
     <font size=15 class="text-center">
     Please input the time when you want to predict the cloud coverage. Timesteps are in 5 min increments. Ex: 6 = 30min
    </font>
  </p>
  <form action="/" method="POST">
    <input type="number" name="time" placeholder="Input Time here">
    <input type="submit">
    <p>Here is your residual output: </p>{{name}}
  </form>
</body>
</html>

内容的提问来源于stack exchange，提问作者jesse lopez