在Django的上下文中设置变量的方法

class CurrentTimeNode2(template.Node):
  def __init__(self, format_string):
    self.format_string = str(format_string)

  def render(self, context):
    now = datetime.datetime.now()
    context['current_time'] = now.strftime(self.format_string)
    return ''

{% current_time2 "%Y-%M-%d %I:%M %p" %}
<p>The time is {{ current_time }}.</p>

{% get_current_time "%Y-%M-%d %I:%M %p" as my_current_time %}
<p>The current time is {{ my_current_time }}.</p>

import re

class CurrentTimeNode3(template.Node):
  def __init__(self, format_string, var_name):
    self.format_string = str(format_string)
    self.var_name = var_name

  def render(self, context):
    now = datetime.datetime.now()
    context[self.var_name] = now.strftime(self.format_string)
    return ''

def do_current_time(parser, token):
  # This version uses a regular expression to parse tag contents.
  try:
    # Splitting by None == splitting by spaces.
    tag_name, arg = token.contents.split(None, 1)
  except ValueError:
    msg = '%r tag requires arguments' % token.contents[0]
    raise template.TemplateSyntaxError(msg)

  m = re.search(r'(.*?) as (\w+)', arg)
  if m:
    fmt, var_name = m.groups()
  else:
    msg = '%r tag had invalid arguments' % tag_name
    raise template.TemplateSyntaxError(msg)

  if not (fmt[0] == fmt[-1] and fmt[0] in ('"', "'")):
    msg = "%r tag's argument should be in quotes" % tag_name
    raise template.TemplateSyntaxError(msg)

  return CurrentTimeNode3(fmt[1:-1], var_name)