Variable lookup

The variable names used in an expr expression are looked up according to the rules described in "Name Lookup" Reference. Looked up values are not "called" as they are when the name attribute is used. In the expressions found in table 1, the name x , func , a , b , obj , age , and status are variable names, while the name meth and title are object attribute names.

Variable names must begin with a letter and contain only letters, digits, and underscore characters. To access a variable with a name that does not follow these rules, it is necessary to use the special variable, _, described in "The special namespace variable, _" below.