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TheTemplate Attribute Language (TAL) is a templating language used to generate dynamicHTML andXML pages. Its main goal is to simplify the collaboration between programmers and designers. This is achieved by embedding TAL statements inside valid HTML (or XML) tags which can then be worked on using common design tools.
TAL was created forZope but is used in otherPython-based projects as well.
The following attributes are used, normally prefixed by "tal:":
tal:attributes="name name; id name" the name and id attributes of an input field could be set to the value of thevariable "name")If a tag has more than one TAL attributes, they are evaluated in the above (fairly logical) order.
In cases when no tag is present which lends itself to take the attributes, special TAL tags can be used, making the "tal:" prefix optional. e.g.:
<tal:ifcondition="context/itemlist">...</tal:if>
would cause the code inside thetal:if tags to be used whenever the context (whatever the application server defines the context to be, e.g. an object) contains variable "itemlist" with atrue value, e.g. a list containing at least one element. The identifier following the colon is arbitrary; it simply needs to be there, and to be the same for the opening and closing tag.
The Macro Expansion Template Attribute Language (METAL) complements TAL, providingmacros which allow the reuse of code across template files. Both were created forZope but are used in otherPython projects as well.
METAL complements TAL with the ability to reuse code. It allows the developer to define and use macros, which in turn may haveslots; when using a macro, variational content can be specified for a slot.
When generatingXML documents, the XML namespace must be specified(xmlns:metal="http://xml.zope.org/namespaces/metal").
The following attributes are recognised, normally requiring a „metal:“ prefix:
Normally, just one of those is used at a time.
In cases when no tag is present which lends itself to take the attributes, and in special cases when more than one METAL attribute is needed, special METAL tags can be used, making the „metal:“ prefix optional. E. g. (sketched withRoundup in mind):
<htmlmetal:define-macro="icing"> ...<metal:myslotdefine-slot="optional-form"> ...</html><htmlmetal:use-macro="templates/page/macros/icing"><formmetal:fill-slot="optional-form"action="."tal:attributes="action context/designator"> ...</form></html>
TAL/TALES/METAL are used by the following projects:
Besides the originalZope implementation, there are (not exhaustive):