day 10 - Filters use a pipe character

Filters use a pipe character

{{ name|lower }}

This displays the value of the {{ name }} variable after being filtered through the lower filter, which converts text to lowercase.

Filters can be chained – that is, they can be used in tandem such that the output of one filter is applied to the next. Here’s an example that takes the first element in a list and converts it to uppercase:

{{ my_list|first|upper }}

Some filters take arguments. A filter argument comes after a colon and is always in double quotes. For example:

{{ bio|truncatewords:"30" }}

This displays the first 30 words of the bio variable.

The following are a few of the most important filters. Appendix E covers the rest.

• addslashes: Adds a backslash before any backslash, single quote, or double quote. This is useful if the produced text is included in a JavaScript string.
• date: Formats a date or datetime object according to a format string given in the parameter, for example:

  {{ pub_date|date:"F j, Y" }}
  

  Format strings are defined in Appendix E.
• length: Returns the length of the value. For a list, this returns the number of elements. For a string, this returns the number of characters. (Python experts, take note that this works on any Python object that knows how to determine its length – i.e., any object that has a __len__() method.)