Question

Flask的新手，试图尝试使用教程，但是render_template()方法中的上下文变量遇到了一些问题。

这里是app.py：

from flask import Flask, render_template, url_for
app = Flask(__name__)

posts = [
    {
        'author': 'Some Author',
        'title': 'Blog Post 1',
        'content': 'First blog post',
        'date_posted': 'April 21, 2018'
    },
    {
        'author': 'Another Author',
        'title': 'Blog Post 2',
        'content': 'Second blog post',
        'date_posted': 'May 21, 2013'
    }
]


@app.route("/")
@app.route("/home")
def home():
    return render_template('home.html', posts=posts)


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


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

这是我的home.html模板：

<!DOCTYPE html>
<html>
<head>
    <title>Home</title>
</head>
<body>
    { % for post in posts % }
        <h4>{{ post.title }}</h4>
        <p>By {{ post.author }} on {{ post.date_posted }}</p>
        <p>{{ post.content }}</p>
    { % endfor % }
</body>
</html>

但是以上操作无效。在页面顶部的浏览器中，

jinja2.exceptions.UndefinedError
jinja2.exceptions.UndefinedError: 'post' is undefined

这也是来自终端的回溯：

File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/bigdaddy/Sites/Flask_Blog/app.py", line 25, in home
    return render_template('home.html', some_list=posts)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/templating.py", line 135, in render_template
    context, ctx.app)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/flask/templating.py", line 117, in _render
    rv = template.render(context)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/jinja2/asyncsupport.py", line 76, in render
    return original_render(self, *args, **kwargs)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/jinja2/environment.py", line 1008, in render
    return self.environment.handle_exception(exc_info, True)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/jinja2/environment.py", line 780, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/jinja2/_compat.py", line 37, in reraise
    raise value.with_traceback(tb)
  File "/home/bigdaddy/Sites/Flask_Blog/templates/home.html", line 8, in top-level template code
    <h4>{{ post.title }}</h4>
  File "/home/bigdaddy/Sites/Flask_Blog/lib/python3.6/site-packages/jinja2/environment.py", line 430, in getattr
    return getattr(obj, attribute)
jinja2.exceptions.UndefinedError: 'post' is undefined

任何帮助将不胜感激。如果有帮助，请在Xubuntu Linux 16.04上的virtualenv中使用python3.6。谢谢

Answer 1

Jinja没有检测到for循环，因为您在{和%之间放置了一个空格，Jinja正在寻找特定的{%对。现在，Jinja完全忽略了{ % for post in posts % }行，将其视为HTML的一部分，无需执行任何操作，而是移至下一个找不到post的行。

以下内容修复了循环的开始和结束：

<body>
    {% for post in posts %}
        <h4>{{ post.title }}</h4>
        <p>By {{ post.author }} on {{ post.date_posted }}</p>
        <p>{{ post.content }}</p>
    {% endfor %}
</body>

Flask上下文变量在模板中不可用

1 个答案: