On Fri, Jul 18, 2014 at 4:45 AM, Neto <paulosouzamac...@gmail.com> wrote:
> Using 'locals ()' would slow page loading? What is better?
>
Using locals() as template context might give you a *slight* slowdown in
template rendering (since you'll have lots of context variables that you
won't be using). However, that effect would be negligible.
There's a much better reason that you shouldn't use locals() as a template
context - it can lead to unexpected side effects and hard-to-debug problems.
If you use locals() as a template context, *every* variable in your local
context - including ones that you've included for counting or other
temporary storage - are used as part of your template rendering. So - lets
say you develop a template that checks {% if foo %}. Intially; your view
doesn't assign anything to foo, so the block doesn't execute. But then, six
months later, you start using a temporary variable foo in your view - all
of a sudden, the template will start rendering the block. You haven't
changed anything in your template - you're just using a temporary variable
that you weren't using before. You didn't *intend* to make a change to your
template; the rendering of the template has changed as result of something
unrelated to the template design.
The Zen of Python says "explicit is better than implicit"; this is a
perfect example of just that. If you're explicit about what you want to
render, and what you pass to a context, this sort of bug will never happen.
Yours,
Russ Magee %-)
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