ColumnizeTag

I wanted to take a long list of objects and display them, but not in an unorder list (way too long) or in a popup/drop-down menu (again, way too long).

This tag will create <tr></tr> and <td></td> tags around everything between the {% columnize %} and {% endcolumnize %} tags. It allows for optional row classes and cell classes.

Tag Parameters

{% columnize num_cols row_tags cell_tags %}{% endcolumnize %}

num_cols: should be greater than 1 (otherwise you aren't creating columns). If it is left out, it defaults to 1

row_tags: is optional. The class name you want for the <tr> tags goes here, otherwise. If you list several (e.g. row1,row2 ) it will loop through them like {% cycle %}. If you do not want row classes, but do want cell classes, pass two quote marks ().

cell_tags: is optional. The class name you want for the <td> tags goes here, otherwise. If you list several (e.g. cell1,cell2 ) it will loop through them within the row like {% cycle %}.

Typical Usage

Simple

<table border="0" cellspacing="5" cellpadding="5">
    {% for o in some_list %}
        {% columnize 3 %}
             <a href="{{ o.get_absolute_url }}">{{ o.name }}</a>
        {% endcolumnize %}
    {% endfor %}
</table>

With row and cell classes

<table border="0" cellspacing="5" cellpadding="5">
    {% for o in some_list %}
        {% columnize 3 myrow mycell %}
             <a href="{{ o.get_absolute_url }}">{{ o.name }}</a>
        {% endcolumnize %}
    {% endfor %}
</table>

With a cell class, but no row class

<table border="0" cellspacing="5" cellpadding="5">
    {% for o in some_list %}
        {% columnize 3 '' mycell %}
             <a href="{{ o.get_absolute_url }}">{{ o.name }}</a>
        {% endcolumnize %}
    {% endfor %}
</table>

Alternating rows, and each cell/column is different

<table border="0" cellspacing="5" cellpadding="5">
    {% for o in some_list %}
        {% columnize 3 row1,row2 cell1,cell2,cell3 %}
             <a href="{{ o.get_absolute_url }}">{{ o.name }}</a>
        {% endcolumnize %}
    {% endfor %}
</table>

Code

from django import template

register = template.Library()

def columnize(parser, token):
    """
        Put stuff into columns. Can also define class tags for rows and cells
        
        Usage: {% columnize num_cols [row_class[,row_class2...]|'' [cell_class[,cell_class2]]] %}
        
        num_cols:   the number of columns to format.
        row_class:  can use a comma (no spaces, please) separated list that cycles 
                    (utilizing the cycle code) can also put in '' for nothing,
                    if you want no row_class, but want a cell_class.
        cell_class: same format as row_class, but the cells only loop within a row.  
                    Every row resets the cell counter.
        
        Typical usage:

        <table border="0" cellspacing="5" cellpadding="5">
        {% for o in some_list %}
        	{% columnize 3 %}
        	<a href="{{ o.get_absolute_url }}">{{ o.name }}</a>
        	{% endcolumnize %}
        {% endfor %}
        </table>
    """
    nodelist = parser.parse(('endcolumnize',))
    parser.delete_first_token()
    
    #Get the number of columns, default 1
    columns = 1
    row_class = ''
    cell_class = ''
    args = token.contents.split(None, 3)
    num_args = len(args)
    if num_args >= 2:
        #{% columnize columns %}
        if args[1].isdigit():
            columns = int(args[1])
        else:
            raise template.TemplateSyntaxError('The number of columns must be a number. "%s" is not a number.') % args[2]
    if num_args >= 3:
        #{% columnize columns row_class %}
        if "," in args[2]:
            #{% columnize columns row1,row2,row3 %}
            row_class = [v for v in args[2].split(",") if v]    # split and kill blanks
        else:
            row_class = [args[2]]
            if row_class == "''":
                # Allow the designer to pass an empty string (two quotes) to skip the row_class and 
                #   only have a cell_class
                row_class = []
    if num_args == 4:
        #{% columnize columns row_class cell_class %}
        if "," in args[3]:
            #{% columnize row_class cell1,cell2,cell3 %}
            cell_class = [v for v in args[3].split(",") if v]    # split and kill blanks
        else:
            cell_class = [args[3]]
            if cell_class == "''":
                # This shouldn't be necessary, but might as well test for it
                cell_class = []

    return ColumnizeNode(nodelist, columns, row_class, cell_class)

class ColumnizeNode(template.Node):
    def __init__(self, nodelist, columns = 1, row_class = '', cell_class = ''):
        self.nodelist = nodelist
        self.columns = int(columns)
        self.counter = 0
        self.rowcounter = -1
        self.cellcounter = -1
        self.row_class_len = len(row_class)
        self.row_class = row_class
        self.cell_class_len = len(cell_class)
        self.cell_class = cell_class
    
    def render(self, context):
        output = ''
        self.counter += 1
        if (self.counter > self.columns):
            self.counter = 1
            self.cellcounter = -1
            
        if (self.counter == 1):
            output = '<tr'
            if self.row_class:
                self.rowcounter += 1
                output += ' class="%s">' % self.row_class[self.rowcounter % self.row_class_len]
            else:
                output += '>'
        
        output += '<td'
        if self.cell_class:
            self.cellcounter += 1
            output += ' class="%s">' % self.cell_class[self.cellcounter % self.cell_class_len]
        else:
            output += '>'
        
        output += self.nodelist.render(context) + '</td>'

        if (self.counter == self.columns):
            output += '</tr>'

        return output

register.tag('columnize', columnize)

A small comment / correction…

Very nice and useful, but produces broken HTML (missing </tr> on last row) if the last row is unfilled (number of cells % columns != 0).

Fix that seems to work for me - replace two lines before the last 'return' with:

        forloop = context['forloop']
        if self.counter == self.columns or forloop['last'] and forloop['counter0'] % self.columns != (self.columns - 1):
            output += '</tr>'