Idea: local variable caching of filters/filter stacks

Migrated issue, originally created by Anonymous

Analyzing the generated .py files from my current project, there's lots of this pattern, as my default_filters are ['h', 'unicode']:

        __M_writer(unicode(filters.html_escape(x)))
        __M_writer(u'some_constant_stuff')
        __M_writer(unicode(filters.html_escape(y)))
        __M_writer(u'more_constant_stuff')
        __M_writer(unicode(filters.html_escape(z)))
        __M_writer(u'even_more_constants')

so it would seem to make sense, to reduce name lookups (in favor of LOAD_FAST) to either

• cache the filter callables as locals in the function (as is being done with __M_writer) to something like
  __M_f_unicode = unicode __M_f_filters__html_escape = filters.html_escape
• and/or maybe better yet create a single cached callable for all of these filter "stacks":
  __M_f_unicode___filters__html_escape = lambda *args,**kwargs: __M_f_unicode(__M_f_filters__html_escape(*args,**kwargs))
  and have the codegen use those instead.

I haven't studied the codegen more deeply to find out what sort of magic this would require though :)

Start with the generated .py pattern shown in the issue and locate the Mako code-generation path that emits filter calls. Compare the proposed local or stacked caching approaches, then verify that generated output preserves filter behavior while reducing repeated name lookups.