@register.tag('for')
def do_for(parser, token):
    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.split(r' *, *', ' '.join(bits[1:in_index]))
    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(('empty', 'endfor',))
    token = parser.next_token()
    if token.contents == 'empty':
        nodelist_empty = parser.parse(('endfor',))
        parser.delete_first_token()
    else:
        nodelist_empty = None
    return ForNode(loopvars, sequence, is_reversed, nodelist_loop, nodelist_empty)
Loops over each item in an array.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/template/defaulttags.py/do_for