how to transfer kwargs to uri_for in template

Question

In my template I have:

<a href="{{ url_for('named_url', slug=x.slug) }}">x.name</a>

In views:

webapp2.Route('/smth/<slug>/', handler=SomeHandler, name='named_url'),

I get this error:

ValueError: URI buiding error: Value "" is not supported for argument "slug".

I also tried:

<a href="{{ url_for('named_url', slug={{x.slug}}) }}">x.name</a>

and

<a href="{{ url_for('named_url', slug='{{x.slug}}') }}">x.name</a>

but it doesn't work. When I print {{x.slug}} somewhere else in the template it prints the correct slug. Also When I hard code slug='some_slug' it also works.

Answer 1

Inside a template variable, you're pretty much in "Python mode". So you would just use the variables directly, missing out both the braces and the quotes:

{{ url_for('named_url', slug=x.slug) }}

Answer 2

I, too, have experienced this ValueError and (through some trial and error) discovered that it is caused by the specified route definition lacking a regular expression.

In other words, try altering your route to be something like:

webapp2.Route('/smth/<slug:.*>/', handler=SomeHandler, name='named_url'),