5.2.7.1 expr="..." attribute

You must supply an expr attribute containing an expression that is evaluated to generate the output src (5.2.7.3) attribute of the <img> tag.

For example:

>>> import albatross
>>> ctx = albatross.SimpleContext('.')
>>> ctx.locals.src = 'httpicons.r.us/spam.png'
>>> albatross.Template(ctx, '<magic>', '''
... <al-img expr="src" whitespace>
... ''').to_html(ctx)
>>> ctx.flush_content()
<img src="httpicons.r.us/spam.png" />