How to set a value of a variable inside a template code

Question

Say I have a template   lt html gt   lt div gt Hello   name    lt  div gt   lt  html gt    While testing it  it would be useful to define the value of the variable without touching the python code that invokes this template  So I m looking for something like this     set name  World           lt html gt   lt div gt Hello   name    lt  div gt   lt  html gt    Does something like this exists in Django

User · Answer

The best solution for this is to write a custom assignment_tag. This solution is more clean than using a with tag because it achieves a very clear separation between logic and styling.

Start by creating a template tag file (eg. appname/templatetags/hello_world.py):

from django import template

register = template.Library()

@register.assignment_tag
def get_addressee():
    return "World"

Now you may use the get_addressee template tag in your templates:

{% load hello_world %}

{% get_addressee as addressee %}

<html>
    <body>
        <h1>hello {{addressee}}</h1>
    </body>
</html>

User · Answer

This is not a good idea in general  Do all the logic in python and pass the data to template for displaying  Template should be as simple as possible to ensure those working on the design can focus on design rather than worry about the logic   To give an example  if you need some derived information within a template  it is better to get it into a variable in the python code and then pass it along to the template

User · Answer

Create a template tag   The app should contain a templatetags directory  at the same level as models py  views py  etc  If this doesn   t already exist  create it - don   t forget the   init   py file to ensure the directory is treated as a Python package   Create a file named define action py inside of the templatetags directory with the following code   from django import template register   template Library     register simple tag def define val None     return val   Note  Development server won   t automatically restart  After adding the templatetags module  you will need to restart your server before you can use the tags or filters in templates     Then in your template you can assign values to the context like this      load define action       if item           define  Edit  as action        else           define  Create  as action        endif      Would you like to   action   this item

User · Answer

An alternative way that doesn t require that you put everything in the  with  block is to create a custom tag that adds a new variable to the context  As in   class SetVarNode template Node       def   init   self  new val  var name           self new val   new val         self var name   var name     def render self  context           context self var name    self new val         return     import re  register tag def setvar parser token         This version uses a regular expression to parse tag contents      try            Splitting by None    splitting by spaces          tag name  arg   token contents split None  1      except ValueError          raise template TemplateSyntaxError    r tag requires arguments    token contents split   0      m   re search r       as   w     arg      if not m          raise template TemplateSyntaxError    r tag had invalid arguments    tag name     new val  var name   m groups       if not  new val 0     new val -1  and new val 0  in                      raise template TemplateSyntaxError    r tag s argument should be in quotes    tag name     return SetVarNode new val 1 -1   var name    This will allow you to write something like this in your template      setvar  a string  as new template var      Note that most of this was taken from here

User · Answer

There are tricks like the one described by John  however  Django s template language by design does not support setting a variable  see the  Philosophy  box in Django documentation for templates   Because of this  the recommended way to change any variable is via touching the Python code

User · Answer

You can use the with template tag      with name  World           lt html gt   lt div gt Hello   name    lt  div gt   lt  html gt     endwith

User · Answer

Perhaps the default template filter wasn t an option back in 2009      lt html gt   lt div gt Hello   name default  World     lt  div gt   lt  html gt

User · Answer

In your template you can do like this      jump link as name       for obj in name         lt div gt   obj helo   -   obj how   lt  div gt     endfor      In your template-tags you can add a tag like this    register assignment tag def jump link        listArr          for i in range 5           listArr append   helo    i  how    i       return listArr

User · Answer

Use the with statement      with total business employees count           total    employee   total pluralize       endwith      I can t imply the code in first paragraph in this answer  Maybe the template language had deprecated the old format

[django] How to set a value of a variable inside a template code?

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