Python Flask没有返回cookie / ValueError：查看函数没有返回响应[重复]

Question

我仍在努力将 Python 中的字符串传递给另一个函数。

我正在尝试遵循此处给出的示例：https://www.tutorialspoint.com/flask/flask_cookies.htm

我试图在我的代码中实现这一点，但我现在得到了以下 Traceback：

  Traceback (most recent call last):
  File "/Users/marcel/tensorflow/lib/python3.6/site-packages/flask/app.py", line 1982, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/marcel/tensorflow/lib/python3.6/site-packages/flask/app.py", line 1615, in full_dispatch_request
    return self.finalize_request(rv)
  File "/Users/marcel/tensorflow/lib/python3.6/site-packages/flask/app.py", line 1630, in finalize_request
    response = self.make_response(rv)
  File "/Users/marcel/tensorflow/lib/python3.6/site-packages/flask/app.py", line 1725, in make_response
    raise ValueError('View function did not return a response')
ValueError: View function did not return a response

这意味着我没有返回任何东西，但我真的看不出哪里出错了，我不得不承认我在这里很迷茫。

我的完整代码如下所示：

from __future__ import print_function
import tensorflow as tf
import argparse
import os
from six.moves import cPickle
from model import Model
from six import text_type
import flask 
from flask import jsonify, render_template, request, make_response

app = flask.Flask(__name__)


@app.route('/')
def index():
    return render_template('index.html')

@app.route('/test')
def tester():
    return "This is a test"

@app.route('/', methods = ['POST', 'GET'])
def main():
    if request.method == 'POST':
        parser = argparse.ArgumentParser(
                           formatter_class=argparse.ArgumentDefaultsHelpFormatter)
        parser.add_argument('--save_dir', type=str, default='save',
                            help='model directory to store checkpointed models')
        parser.add_argument('-n', type=int, default=500,
                            help='number of characters to sample')
        parser.add_argument('--prime', type=text_type, default=u' ',
                            help='prime text')
        parser.add_argument('--sample', type=int, default=1,
                            help='0 to use max at each timestep, 1 to sample at '
                                 'each timestep, 2 to sample on spaces')

        args = parser.parse_args()

        resp = make_response(render_template('sample.html'))
        resp.set_cookie('args', args)

        return resp


@app.route('/sampler', methods = ['POST', 'GET'])
def sample():
    args = request.cookies.get('args')
    with open(os.path.join(args.save_dir, 'config.pkl'), 'rb') as f:
        saved_args = cPickle.load(f)
    with open(os.path.join(args.save_dir, 'chars_vocab.pkl'), 'rb') as f:
        chars, vocab = cPickle.load(f)
    model = Model(saved_args, training=False)
    with tf.Session() as sess:
        tf.global_variables_initializer().run()
        saver = tf.train.Saver(tf.global_variables())
        ckpt = tf.train.get_checkpoint_state(args.save_dir)
        if ckpt and ckpt.model_checkpoint_path:
            saver.restore(sess, ckpt.model_checkpoint_path)
            if request.method == 'POST':
                text = model.sample(sess, chars, vocab, args.n, args.prime,
                                   args.sample).encode('utf-8')
                resp = make_response(render_template('text.html'))
                resp.set_cookie('verse', text)
                return resp


@app.route('/text')
def printer():    
    verse = request.cookies.get('verse')
    return verse


@app.errorhandler(404)
def page_not_found(error):
    return render_template('404.html'), 404

if __name__ == '__main__':
    main()

在我尝试将 cookie 从示例函数发送到打印机函数之前，但它返回了相同的错误。

我之前的代码：

def sample(args):
    with open(os.path.join(args.save_dir, 'config.pkl'), 'rb') as f:
        saved_args = cPickle.load(f)
    with open(os.path.join(args.save_dir, 'chars_vocab.pkl'), 'rb') as f:
        chars, vocab = cPickle.load(f)
    model = Model(saved_args, training=False)
    with tf.Session() as sess:
        tf.global_variables_initializer().run()
        saver = tf.train.Saver(tf.global_variables())
        ckpt = tf.train.get_checkpoint_state(args.save_dir)
        if ckpt and ckpt.model_checkpoint_path:
            saver.restore(sess, ckpt.model_checkpoint_path)
            text = model.sample(sess, chars, vocab, args.n, args.prime,
                               args.sample).encode('utf-8')
            resp = make_response(render_template('text.html'))
            resp.set_cookie('verse', text)
            return resp


@app.route('/text')
def printer():    
    verse = request.cookies.get('verse')
    return verse

Answer 1

当verse cookie 值不存在时，verse 变量的值将变为None。这意味着您的 text 视图将返回 None，Flask 不喜欢并理解为“视图函数没有返回响应”。

您可能需要正确处理这种情况 - 例如，只需返回一个空字符串即可解决问题（当然，这只是一个简单的修复示例，以展示差异）：

@app.route('/text')
def printer():    
    return request.cookies.get('verse', '')

此外，并非sample() 视图中的所有代码路径都返回有效响应 - 确保也解决它（例如，向 sample() 视图发出 GET 请求将导致相同的“视图函数没有返回响应”错误）。

Answer 2

在main中，需要返回一个超出请求参数检查范围的值：

@app.route('/', methods = ['POST', 'GET'])
def main():
   if request.method == 'POST':
       parser = argparse.ArgumentParser(
       ....#statements follow            
       args = parser.parse_args()

       resp = make_response(render_template('sample.html'))
       resp.set_cookie('args', args)

       return resp
  return render_template('home.html') #need to return something here