tal:condition ------------- Syntax: ``tal:condition="expression"`` Description: If the expression evaluates to true then this tag and all its children will be output. If the expression evaluates to false then this tag and all its children will not be included in the output. Example::

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tal:repeat ---------- Syntax: ``tal:repeat="name expression"`` Description: Evaluates "expression", and if it is a sequence, repeats this tag and all children once for each item in the sequence. The "name" will be set to the value of the item in the current iteration, and is also the name of the repeat variable. The repeat variable is accessible using the TAL path: repeat/name and has the following properties: * index - Iteration number starting from zero * number - Iteration number starting from one * even - True if this is an even iteration * odd - True if this is an odd iteration * start - True if this is the first item in the sequence * end - True if this is the last item in the sequence. For iterators this is never true * length - The length of the sequence. For iterators this is maxint as the length of an iterator is unknown * letter - The lower case letter for this iteration, starting at "a" * Letter - Upper case version of letter * roman - Iteration number in Roman numerals, starting at i * Roman - Upper case version of roman Example::

tal:content ----------- Syntax: ``tal:content="[text | structure] expression"`` Description: Replaces the contents of the tag with the value of "expression". By default, and if the "text" keyword is present, then the value of the expression will be escaped as required (i.e. characters "&<> will be escaped). If the "structure" keyword is present then the value will be output with no escaping performed. Example::

tal:replace ----------- Syntax: ``tal:replace="[text | structure] expression"`` Description: Behaves identically to tal:content, except that the tag is removed from the output (as if tal:omit-tag had been used). Example::

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tal:attributes -------------- Syntax: ``tal:attributes="name expression[;attributes-expression]"`` Description: Evaluates each "expression" and replaces the tag's attribute "name". If the expression evaluates to nothing then the attribute is removed from the tag. If the expression evaluates to default then the original tag's attribute is kept. If the "expression" requires a semi-colon then it must be escaped by using ";;". Example:: Your Homepage tal:omit-tag ------------ Syntax: ``tal:omit-tag="expression"`` Description: Removes the tag (leaving the tags content) if the expression evaluates to true. If expression is empty then it is taken as true. Example::

Welcome to this page! TALES Expressions ================= The expressions used in TAL are called TALES expressions. The simplest TALES expression is a path which references a value, e.g. page/body references the body property of the page object. path ---- Syntax: ``[path:]string[|TALES Expression]`` Description: A path, optionally starting with the modifier 'path:', references a property of an object. The '/' delimiter is used to end the name of an object and the start of the property name. Properties themselves may be objects that in turn have properties. The '|' ("or") character is used to find an alternative value to a path if the first path evaluates to 'Nothing' or does not exist. Example::

There are several built in paths that can be used in paths: * nothing - acts as None in Python * default - keeps the existing value of the node (tag content or attribute value) * options - the dictionary of values passed to the template (through the Context __init__ method) * repeat - access the current repeat variable (see tal:repeat) * attrs - a dictionary of original attributes of the current tag * CONTEXTS - a dictionary containing all of the above exists ------ Syntax: ``exists:path`` Description: Returns true if the path exists, false otherwise. This is particularly useful for removing tags from output when the tags will have no content. Example::

nocall ------ Syntax: ``nocall:path`` Description: Returns a reference to a path, but without evaluating the path. Useful when you wish to define a new name to reference a function, not the current value of a function. Example::

not --- Syntax: ``not:tales-path`` Description: Returns the inverse of the tales-path. If the path returns true, ``not:path`` will return false. Example::

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string ------ Syntax: ``string:text`` Description: Evaluates to a literal string with value text while substituting variables with the form ``${pathName}`` and ``$pathName`` Example:: python ------ Syntax: ``python:python-code`` Description: Evaluates the python-code and returns the result. The python code must be properly escaped, e.g. "python: 1 < 2" must be written as "python: 1 < 2". The python code has access to all Python functions, including four extra functions that correspond to their TALES commands: path (string), string (string), exists (string), and nocall (string) Example::

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METAL Macro Language ==================== METAL is a macro language commonly used with TAL and TALES. METAL allows part of a template to be used as a macro in later parts of a template, or a separate template altogether. metal:define-macro ------------------ Syntax: ``metal:define-macro="name"`` Description: Defines a new macro that can be reference later as "name". Example::

metal:use-macro --------------- Syntax: ``metal:use-macro="expression"`` Description: Evaluates "expression" and uses this as a macro. Example::

metal:define-slot ----------------- Syntax: ``metal:define-slot="name"`` Description: Defines a customisation point in a macro with the given name. Example::

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metal:fill-slot --------------- Syntax: ``metal:fill-slot="name"`` Description: Replaces the content of a slot with this element. Example::

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