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Tag Archive » ‘leah-culver’

Displaying stars (with rounding) as a Django templatetag

October 2nd, 2007

Since my last post was quite popular (by my simple blogging standards), I’ve decided to post another Django snippet that I’ve used while coding WeGoEat. (I know, I know… one of these days I’ll finish. I’ve just been really, really lazy busy.)

After reading Leah’s blog (of Pownce fame) about “rounding to the nearest half”, I was immediately struck by two sobering realities:

  1. I would need that exact same algorithm for my current site.
  2. A few years out of grad school, and I couldn’t even begin to fathom a solution. Thank you, Internet.

In any case, I figured I’d wrap my solution into a template tag that people could use/steal/copy. Here’s a generated test page that illustrates what my template tag would display.

Stars!

You can even customize the display a bit:

25 Stars!

I know, I know… I can do a lot better. ;) In any case, here’s the code snippet that I placed in a file called show_stars.py:

import math
 
from django.template import Library, Node, TemplateSyntaxError, VariableDoesNotExist, resolve_variable
from django.conf import settings
 
register = Library()
 
IMG_TEMPLATE = '<img src="%s" alt="%s"/>'
 
PATH_TO_WHOLE_STAR = IMG_TEMPLATE % (settings.MEDIA_URL + 'img/stars/star.png', "Whole Star")
PATH_TO_THREE_QUARTER_STAR = IMG_TEMPLATE % (settings.MEDIA_URL + 'img/stars/three-quarter.png', "3/4 Star")
PATH_TO_HALF_STAR = IMG_TEMPLATE % (settings.MEDIA_URL + 'img/stars/half.png', "1/2 Star")
PATH_TO_QUARTER_STAR = IMG_TEMPLATE % (settings.MEDIA_URL + 'img/stars/quarter.png', "1/4 Star")
PATH_TO_BLANK_STAR = IMG_TEMPLATE % (settings.MEDIA_URL + 'img/stars/blank.png', "Empty Star")
 
class ShowStarsNode(Node):
    """ Default rounding is to the whole unit """
    def __init__(self, context_var, total_stars, round_to):
        self.context_var = context_var
        self.total_stars = int(total_stars)
        self.round_to = round_to.lower()
 
    def render(self, context):
        try:
            stars = resolve_variable(self.context_var, context)
        except VariableDoesNotExist:
            return ''
 
        if self.round_to == "half":
            stars = round(stars*2)/2
        elif self.round_to == "quarter":
            stars = round(stars*4)/4
        else:
            stars = round(stars)
 
        fraction, integer = math.modf(stars)
        integer = int(integer)
        output = []
 
        for whole_star in range(integer):
            output.append(PATH_TO_WHOLE_STAR)
        if self.round_to == 'half' and fraction == .5:
            output.append(PATH_TO_HALF_STAR)
        elif self.round_to == 'quarter':
            if fraction == .25:
                output.append(PATH_TO_QUARTER_STAR)
            elif fraction == .5:
                output.append(PATH_TO_HALF_STAR)
            elif fraction == .75:
                output.append(PATH_TO_THREE_QUARTER_STAR)
 
        if fraction:
            integer += 1
 
        blanks = int(self.total_stars - integer)
 
        for blank_star in range(blanks):
            output.append(PATH_TO_BLANK_STAR)
 
        return "".join(output)
 
""" show_stars context_var of 5 round to half """
def do_show_stars(parser, token):
    args = token.contents.split()
    if len(args) != 7:
        raise TemplateSyntaxError('%s tag requires exactly six arguments' % args[0])
    if args[2] != 'of':
        raise TemplateSyntaxError("second argument to '%s' tag must be 'of'" % args[0])
    if args[4] != 'round':
        raise TemplateSyntaxError("fourth argument to '%s' tag must be 'round'" % args[0])
    if args[5] != 'to':
        raise TemplateSyntaxError("fourth argument to '%s' tag must be 'to'" % args[0])
    return ShowStarsNode(args[1], args[3], args[6])   
 
register.tag('show_stars', do_show_stars)

I’ve also wrapped up the star graphics I used. A big ups to the Silk Icons creator. ;) For those of you that don’t care for .zip files, here’s all the star images I used:

Blankquarterhalfthree quarterfull

To use the tag, it’ll look something like this in your templates:

{% load show_stars %}
     {% show_stars context_var of 5 round to half %}
{% endif %}

Note: You can change the following:

  1. context_var is whatever var contains the value you want rounded (it was ‘value’ in the screenshots)
  2. 5 can be any integer; this is the maximum number of stars to display. I should probably check to make sure you don’t put a number smaller than context_var, but I’ll leave that up to you. ;)
  3. half can be any of the following values: whole, half, or quarter
  4. Make sure to edit the paths to the star files in the templatetag file

And since this is on my blog, feel totally free to take/use/steal/distribute/copy/modify any code you see fit. All I ask is if you find any bugs, have any comments, or can think of ways to make my ugly code cleaner – I’d love to hear from you. :)

Enjoy!

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