I am trying to output the first 255 characters of a description on a list of items and am looking for a method to get that.
Example: I have a variable that contains 300
A more simple way by using the standard template tag is:
{{ variable|stringformat:".10s" }}
In this case the 10 is the position argument and for a string it is the maximum number of characters to be displayed.
If the "my_variable" is a string, you can take advantage of the slice filter, which treats the string as a list of characters. If it's a set of words, the rough equivilant is truncatewords - but that doesn't quite sound like your need.
truncatewords
also adds an ellipsis ...
at the end of the truncated result.
Usage would be something like
{{ my_variable|slice:":255" }}
If do you want to truncate by word, take a look at this https://docs.djangoproject.com/en/1.4/ref/templates/builtins/#truncatechars
There is an official built-in filter:
{{ variable|truncatechars:255 }}
It doesn't exist unfortunately. There are moves to implement it, but it's still in the design stage (well, implemented, but waiting for design decision), as described here.
Patch attached to that ticket contains implementation.
Using a templatefilter for truncating your text isn't really suitable for a responsive design. Therefore you could also use css to truncate your text that is responsive. I know the OP asked to do this with a django templatefilter.
You can achieve a responsive truncated text using this:
.class {
width: 100%;
white-space: nowrap;
overflow: hidden;
text-overflow: ellipsis;
}