This attribute must the specified. It contains an expression that is evaluated when the template is executed and the result is written as a string to the output.
For example:
>>> import albatross >>> ctx = albatross.SimpleContext('.') >>> ctx.locals.items = ['pencil', 'eraser', 'lunchbox'] >>> albatross.Template(ctx, '<magic>', ''' ... There are <al-value expr="len(items)" whitespace> items ... ''').to_html(ctx) >>> ctx.flush_content() There are 3 items