8.14. Interpreter
EN: Interpreter
PL: Interpreter
Type: class
The Interpreter design pattern is a behavioral design pattern that specifies how to evaluate sentences in a language. This pattern is used to interpret sentences in a language and represents a grammar as a hierarchy of composite objects.
In Python, we can implement the Interpreter pattern using classes. Here's a simple example:
First, we define an AbstractExpression class that declares an abstract
interpret method:
>>> class AbstractExpression:
... def interpret(self):
... pass
Then, we define a TerminalExpression class that implements the interpret
method:
>>> class TerminalExpression(AbstractExpression):
... def interpret(self):
... print("Terminal expression is being interpreted.")
Finally, we can use the AbstractExpression and TerminalExpression classes
like this:
>>> class NonterminalExpression(AbstractExpression):
... def __init__(self, expression):
... self._expression = expression
...
... def interpret(self):
... print("Nonterminal expression is being interpreted.")
... self._expression.interpret()
...
>>> terminal_expression = TerminalExpression()
>>> nonterminal_expression = NonterminalExpression(terminal_expression)
...
>>> nonterminal_expression.interpret()
Nonterminal expression is being interpreted.
Terminal expression is being interpreted.
In this example, the NonterminalExpression interprets a TerminalExpression.
8.14.1. Pattern
8.14.2. Problem
8.14.3. Solution