Django: How can I get a block from a template?

Suppose my template has in it something like {% block subject %}my subject{% endblock %} and I load this templa开发者_如何学JAVAte with tmpl = loader.get_template('mytemplate.html'), how can I extract "my subject"?

---

Camilo's solution doesn't work when your template extends a base. I've modified it a bit to (hopefully) fix that problem:

from django.template import Context
from django.template.loader import get_template
from django.template.loader_tags import BlockNode, ExtendsNode

def _get_node(template, context=Context(), name='subject'):
    for node in template:
        if isinstance(node, BlockNode) and node.name == name:
            return node.render(context)
        elif isinstance(node, ExtendsNode):
            return _get_node(node.nodelist, context, name)
    raise Exception("Node '%s' could not be found in template." % name)

I'm really not sure if this is the right way to recursively iterate over all the nodes... but it works in my limited case.

---

from django.template import Context
from django.template.loader import get_template
from django.template.loader_tags import BlockNode

t = get_template('template.html')
for node in t:
    if isinstance(node, BlockNode) and node.name == 'subject':
        print node.render(Context())

This worked for me, using Django 1.1.1

---

The proposed answers don't work since Django 1.8:

Changed in Django 1.8: get_template() returns a backend-dependent Template instead of a django.template.Template.

The new django.template.backends.django.Template isn't iterable, so a for loop gives the error:

'Template' object is not iterable.

A solution for those who use Django template system (based on @CamiloDíazRepka answer):

from django.template import Context
from django.template.loader import get_template
from django.template.loader_tags import BlockNode

t = get_template('template.html')
for node in t.template:
    if isinstance(node, BlockNode) and node.name == 'subject':
        print node.render(Context())

---

I wanted this to make an include tag that gets only a section of the template in question. I'm sharing it here just in case someone else wanted it for the same reason.

Usage: {% include_block "template.html" "block_name" %}

@register.tag
def include_block(parser, token):
    try:
        tag_name, include_file, block_name = token.split_contents()
    except ValueError:
        raise template.TemplateSyntaxError("%r tag requires a two arguments" % (token.contents.split()[0]))

    #pass vars with stripped quotes 
    return IncludeBlockNode(include_file.replace('"', ''), block_name.replace('"', ''))

class IncludeBlockNode(template.Node):
    def __init__(self, include_file, block_name):
        self.include_file = include_file
        self.block_name = block_name

    def _get_node(self, template, context, name):
        '''
        taken originally from
        http://stackoverflow.com/questions/2687173/django-how-can-i-get-a-block-from-a-template
        '''
        for node in template:
            if isinstance(node, BlockNode) and node.name == name:
                return node.nodelist.render(context)
            elif isinstance(node, ExtendsNode):
                return self._get_node(node.nodelist, context, name)

        raise Exception("Node '%s' could not be found in template." % name)

    def render(self, context):
        t = get_template(self.include_file)
        return self._get_node(t, context, self.block_name)