process-template-context (context, template=None)

This event is emitted right before a template is rendered and can be used to inject values directly into the template context. The context is always provided and is a dictionary that can be modified.

What's important to know that this is not the only way to modify the template context. Another one is to modify the underlying Jinja Environment on the environment directly. The difference is that the globals from the jinja_env are available in all templates whereas the modified template context is only available in the toplevel template. This becomes apparent when you are dealing with imported template macros. A macro will not have access to values you provide here unless they are explicitly passed to it.

The filename of the template is passed as template but is only available if the template was indeed loaded from the templates folder. There are many more places where templates are rendered in those cases the value will not be provided.

Example

def on_process_template_context(self, context, **extra):
    context['my_variable'] = 'my value'