Invalid Block Tag i=0, in Django
I was going through Appengine's Getting Started guide for python, while reading up templates,I modified the code(which is a simple guestbook) to include simple numbering next to the guestbook entries.
In index.html i added the (what I thought would be) relevant code.
index.html (I have added {%i=0%} on line 3,{%i+=1%} on line 5, and {{i}} on line 7, the rest is from the guide):
<html>
<body>
{%i=0%}
{% for greeting in greetings %}
{%i+=1%}
{% if greeting.author %}
<b>{{i}}:{{ greeting.author.nickname }}</b> wrote:
{% else %}
An anonymous person wrote:
{% endif %}
<blockquote>{{ greeting.content|escape }}</blockquote>
{% endfor %}
<form action="/sign" method开发者_StackOverflow中文版="post">
<div><textarea name="content" rows="3" cols="60"></textarea></div>
<div><input type="submit" value="Sign Guestbook"></div>
</form>
<a href="{{ url }}">{{ url_linktext }}</a>
</body>
</html>
I got the following error
TemplateSyntaxError: Invalid block tag: 'i=0'
I read up Django's help on templates, which says that
The Django template system provides tags which function similarly to some programming constructs – an if tag for boolean tests, a for tag for looping, etc. – but these are not simply executed as the corresponding Python code, and the template system will not execute arbitrary Python expressions.
So I guess, that performing calculations is not what the templating system is for.
tl;dr
Can anyone tell me how to number my entries or use the "counter - increment" construct using Django templates?
I don't thing this code is necessary, but to complete the picture,
Unchanged helloworld.py code:
import os
from google.appengine.ext.webapp import template
import cgi
from google.appengine.api import users
from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
from google.appengine.ext import db
class Greeting(db.Model):
author = db.UserProperty()
content = db.StringProperty(multiline=True)
date = db.DateTimeProperty(auto_now_add=True)
class MainPage(webapp.RequestHandler):
def get(self):
greetings_query = Greeting.all().order('-date')
greetings = greetings_query.fetch(10)
if users.get_current_user():
url = users.create_logout_url(self.request.uri)
url_linktext = 'Logout'
else:
url = users.create_login_url(self.request.uri)
url_linktext = 'Login'
template_values = {
'greetings': greetings,
'url': url,
'url_linktext': url_linktext,
}
path = os.path.join(os.path.dirname(__file__), 'index.html')
self.response.out.write(template.render(path, template_values))
class Guestbook(webapp.RequestHandler):
def post(self):
greeting = Greeting()
if users.get_current_user():
greeting.author = users.get_current_user()
greeting.content = self.request.get('content')
greeting.put()
self.redirect('/')
application = webapp.WSGIApplication(
[('/', MainPage),
('/sign', Guestbook)],
debug=True)
def main():
run_wsgi_app(application)
if __name__ == "__main__":
main()
From http://www.djangobook.com/en/beta/chapter04/
{% for item in todo_list %}
<p>{{ forloop.counter }}: {{ item }}</p>
{% endfor %}
It depends on what you need it for. If you need the actual count, you can use a for loop in the template: http://docs.djangoproject.com/en/dev/ref/templates/builtins/#for
Then you can use forloop.counter or forloop.counter0 to check the index.
If you just want to display a list of numbers you can use a html ordered list.
Django's template engine is for design only, and you want to keep calculations out of it. If you need to do something with your data at the template layer you can write a custom tag/filter.
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