This is a customized version of the default for
template tag which takes an optional {% else %}
clause that will be displayed if the given array is empty.
from django.template import *
>>> t1 = Template("""
{% load mytags %}
{% for athlete in athlete_list %}
{{ athlete }}
{% else %}
No athlete in list!
{% endfor %}
""")
>>> c1 = Context(
{'athlete_list':
['me', 'myself', 'I']
})
>>> t1.render(c1)
u'me myself I '
>>> c2 = Context({})
>>> t1.render(c2)
u'No athlete in list!'
If you want to automatically override the builtin for
template-tag add it to the builtins:
from django.template import add_to_builtins
add_to_builtins('python.path.to.mytags')
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 | import re
try:
reversed
except NameError:
from django.utils.itercompat import reversed # Python 2.3 fallback
from django.template import Node, NodeList, Library
from django.template import TemplateSyntaxError, VariableDoesNotExist
from django.conf import settings
register = Library()
class ForNode(Node):
def __init__(self, loopvars, sequence, is_reversed, nodelist_loop, nodelist_false):
self.loopvars, self.sequence = loopvars, sequence
self.is_reversed = is_reversed
self.nodelist_loop, self.nodelist_false = nodelist_loop, nodelist_false
def __repr__(self):
reversed_text = self.is_reversed and ' reversed' or ''
return "<For Node: for %s in %s, tail_len: %d%s>" % \
(', '.join(self.loopvars), self.sequence, len(self.nodelist_loop),
reversed_text)
def __iter__(self):
for node in self.nodelist_loop:
yield node
for node in self.nodelist_false:
yield node
def get_nodes_by_type(self, nodetype):
nodes = []
if isinstance(self, nodetype):
nodes.append(self)
nodes.extend(self.nodelist_loop.get_nodes_by_type(nodetype))
nodes.extend(self.nodelist_false.get_nodes_by_type(nodetype))
return nodes
def render(self, context):
nodelist = NodeList()
if 'forloop' in context:
parentloop = context['forloop']
else:
parentloop = {}
context.push()
try:
values = self.sequence.resolve(context, True)
except VariableDoesNotExist:
values = []
if values is None:
values = []
if not hasattr(values, '__len__'):
values = list(values)
len_values = len(values)
if len_values < 1:
return self.nodelist_false.render(context)
if self.is_reversed:
values = reversed(values)
unpack = len(self.loopvars) > 1
# Create a forloop value in the context. We'll update counters on each
# iteration just below.
loop_dict = context['forloop'] = {'parentloop': parentloop}
for i, item in enumerate(values):
# Shortcuts for current loop iteration number.
loop_dict['counter0'] = i
loop_dict['counter'] = i+1
# Reverse counter iteration numbers.
loop_dict['revcounter'] = len_values - i
loop_dict['revcounter0'] = len_values - i - 1
# Boolean values designating first and last times through loop.
loop_dict['first'] = (i == 0)
loop_dict['last'] = (i == len_values - 1)
if unpack:
# If there are multiple loop variables, unpack the item into
# them.
context.update(dict(zip(self.loopvars, item)))
else:
context[self.loopvars[0]] = item
for node in self.nodelist_loop:
nodelist.append(node.render(context))
if unpack:
# The loop variables were pushed on to the context so pop them
# off again. This is necessary because the tag lets the length
# of loopvars differ to the length of each set of items and we
# don't want to leave any vars from the previous loop on the
# context.
context.pop()
context.pop()
return nodelist.render(context)
def do_for(parser, token):
"""
Loops over each item in an array, with support of ``else``.
For example, to display a list of athletes given ``athlete_list``::
<ul>
{% for athlete in athlete_list %}
<li>{{ athlete.name }}</li>
{% endfor %}
</ul>
You can loop over a list in reverse by using
``{% for obj in list reversed %}``.
You can also unpack multiple values from a two-dimensional array::
{% for key,value in dict.items %}
{{ key }}: {{ value }}
{% endfor %}
As you can see, this customized ``for`` tag can take an optional
``{% else %}`` clause that will be displayed if the given array is empty::
<ul>
{% for athlete in athlete_list %}
<li>{{ athlete.name }}</li>
{% else %}
<li>Sorry, no athlete in this list!</li>
{% endfor %}
<ul>
The for loop sets a number of variables available within the loop:
========================== ================================================
Variable Description
========================== ================================================
``forloop.counter`` The current iteration of the loop (1-indexed)
``forloop.counter0`` The current iteration of the loop (0-indexed)
``forloop.revcounter`` The number of iterations from the end of the
loop (1-indexed)
``forloop.revcounter0`` The number of iterations from the end of the
loop (0-indexed)
``forloop.first`` True if this is the first time through the loop
``forloop.last`` True if this is the last time through the loop
``forloop.parentloop`` For nested loops, this is the loop "above" the
current one
========================== ================================================
"""
bits = token.contents.split()
if len(bits) < 4:
raise TemplateSyntaxError("'for' statements should have at least four"
" words: %s" % token.contents)
is_reversed = bits[-1] == 'reversed'
in_index = is_reversed and -3 or -2
if bits[in_index] != 'in':
raise TemplateSyntaxError("'for' statements should use the format"
" 'for x in y': %s" % token.contents)
loopvars = re.sub(r' *, *', ',', ' '.join(bits[1:in_index])).split(',')
for var in loopvars:
if not var or ' ' in var:
raise TemplateSyntaxError("'for' tag received an invalid argument:"
" %s" % token.contents)
sequence = parser.compile_filter(bits[in_index+1])
nodelist_loop = parser.parse(('else', 'endfor',))
token = parser.next_token()
if token.contents == 'else':
nodelist_false = parser.parse(('endfor',))
parser.delete_first_token()
else:
nodelist_false = NodeList()
#parser.delete_first_token()
return ForNode(loopvars, sequence, is_reversed, nodelist_loop, nodelist_false)
do_for = register.tag("for", do_for)
|
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