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Flask Mega Tutorial - jinja2.exceptions.UndefinedError: 'form' undefined

I am working on a Meguel Tutorial Miguel Grinberg Flask Mega Tutorial and I cannot understand why the index page is no longer loading. Here is the trace:

File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__ return self.wsgi_app(environ, start_response) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app response = self.make_response(self.handle_exception(e)) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception reraise(exc_type, exc_value, tb) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app response = self.full_dispatch_request() File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request rv = self.handle_user_exception(e) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception reraise(exc_type, exc_value, tb) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request rv = self.dispatch_request() File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request return self.view_functions[rule.endpoint](**req.view_args) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask_login.py", line 658, in decorated_view return func(*args, **kwargs) File "/home/asdoylejr/microblog/app/views.py", line 44, in index posts = posts) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/templating.py", line 128, in render_template context, ctx.app) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/flask/templating.py", line 110, in _render rv = template.render(context) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 969, in render return self.environment.handle_exception(exc_info, True) File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 742, in handle_exception reraise(exc_type, exc_value, tb) File "/home/asdoylejr/microblog/app/templates/index.html", line 2, in top-level template code {% extends "base.html" %} File "/home/asdoylejr/microblog/app/templates/base.html", line 30, in top-level template code {% block content %}{% endblock %} File "/home/asdoylejr/microblog/app/templates/index.html", line 7, in block "content" {{form.hidden_tag()}} File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 397, in getattr return getattr(obj, attribute) UndefinedError: 'form' is undefined

Here is the code for the specified index page:

 <!-- extend base layout --> {% extends "base.html" %} {% block content %} <h1>Hi, {{g.user.nickname}}!</h1> <form action="" method="post" name="post"> {{form.hidden_tag()}} <table> <tr> <td>Say something:</td> <td>{{form.post(size = 30, maxlength = 140)}}</td> <td> {% for error in form.errors.post %} <span style="color: red;">[{{error}}]</span><br> {% endfor %} </td> </tr> <tr> <td></td> <td><input type="submit" value="Post!"></td> <td></td> </tr> </table> </form> {% for post in posts %} <p> {{post.author.nickname}} says: <b>{{post.body}}</b> </p> {% endfor %} {% endblock %}

And here is the code in the view:

 @app.route('/', methods = ['GET', 'POST']) @app.route('/index', methods = ['GET', 'POST']) @login_required def index(): form = PostForm() if form.validate_on_submit(): post = Post(body = form.post.data, timestamp = datetime.utcnow(), author = g.user) db.session.add(post) db.session.commit() flash('Your post is now live!') return redirect(url_for('index')) posts = g.user.followed_posts().all() return render_template("index.html", title = 'Home', user = user, posts = posts)

I read the tutorial several times and compared my code with the source that it releases at the end of each lesson, and I have no idea why it doesn't work. I am not sure why he had problems submitting a form in this view when he does not return an error transmission form in another view.

Can someone point me in the right direction?

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2 answers

The error message you received is explained in the stack trace. In particular, here:

 File "/home/asdoylejr/microblog/app/templates/index.html", line 7, in block "content" {{form.hidden_tag()}} File "/home/asdoylejr/microblog/flask/lib/python2.7/site-packages/jinja2/environment.py", line 397, in getattr return getattr(obj, attribute) UndefinedError: 'form' is undefined

The error message comes from Jinja, who says that form is undefined. Your template is trying to use form ...

 ... {% block content %} <h1>Hi, {{g.user.nickname}}!</h1> <form action="" method="post" name="post"> {{form.hidden_tag()}} <table> ...

... but you never passed it as part of your render_template method (you only defined title , user and posts ) ...

 return render_template("index.html", title = 'Home', user = user, posts = posts)
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You must pass form as a context variable. Try the following:

 @app.route('/', methods = ['GET', 'POST']) @app.route('/index', methods = ['GET', 'POST']) @login_required def index(): form = PostForm() if form.validate_on_submit(): post = Post(body = form.post.data, timestamp = datetime.utcnow(), author = g.user) db.session.add(post) db.session.commit() flash('Your post is now live!') return redirect(url_for('index')) posts = g.user.followed_posts().all() return render_template("index.html", title = 'Home', user = user, posts = posts, form = form)
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Source: https://habr.com/ru/post/956450/

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