Re: Thread-safeness of templates

To add to your example.  Default arguments are parsed once by the interpreter, not each time the program is run.  Most folks don't desire side effects like this.  One way to avoid it is to only use immutable types in python as keyword arguments (True, False, None, numbers, strings, tuples).

Brian

On Tue, Oct 4, 2011 at 7:23 PM, Martin J. Laubach <google@emsi.priv.at> wrote:

  Are you sure your context is thread-safe, ie. it's rebuilt from scratch every time you render an email and not re-used, stored in a global variable, class variable, whatever? Your problem description very much sounds like someone is fiddling with the context while the template is rendering.

  A popular way to generate such a problem would be to use a literal dict as default parameter, something like:

    def my_render_email(recipient, context={}):

        context['email'] = recipient

        body = render_to_string('template.html', context) 

        ...

  That is absolutely positively guaranteed to blow up in your face when you least expect it.

        mjl

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Brian Bouterse
ITng Services

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