Class TemplateEval

Return the eval-result of expr or a "fallback"-value.

Use this in the template to use default-values for optional data.
The default-value is used if 'expr' does not exist/is invalid/results in None.

:Note: the variable-name has to be quoted! (like in eval)

:Example:
    ::
        @! default("optional_var","fallback_value") !@
        <!--(if default("optional",False))-->"YES"<!--(else)-->"NO"<!--(end)-->
        <!--(for i in default("optional_list",[]))-->

Test if a variable exists.

This tests if 'varname' exists in the current locals-namespace.

:Note: the variable-name has to be quoted! (like in eval)

This only works for single variable names. If you want to test complicated expressions, use i.e. _default. (i.e. _default("expr",False))