MVC是一个非常重要的设计模式，用于将应用组织成三个部分：模型、视图和控制器。同时，MVC也是一种架构模式，比如流行的 Django 框架就是 MVC(MTV) 模式。
每个部分都有明确的职责。模型负责访问数据，管理应用的状态。视图是模型的外在表现。视图并非必须是图形化的；文本输出也是一种好视图。控制器是模型与视图之间的连接。 MVC的恰当使用能确保最终产出的应用易于维护、易于扩展。
示例如下：
quotes = ('A man is not complete until he is married. Then he is finished.',
'As I said before, I never repeat myself.',
'Behind a successful man is an exhausted woman.',
'Black holes really suck...', 'Facts are stubborn things.')
class QuoteModel:
def get_quote(self, n):
try:
value = quotes[n]
except IndexError as e:
value = 'Not found!'
return value
class QuoteTerminalView:
def show(self, quote):
print('And the quote is: "{}"'.format(quote))
def error(self, msg):
print('Error: {}'.format(msg))
def select_quote(self):
return input('Which quote number would you like to see? ')
class QuoteTerminalController:
def __init__(self):
self.model = QuoteModel()
self.view = QuoteTerminalView()
def run(self):
valid_input = False
while not valid_input:
n = self.view.select_quote()
try:
n = int(n)
except ValueError as e:
self.view.error("Incorrect index '{}'".format(n))
else:
valid_input = True
quote = self.model.get_quote(n)
self.view.show(quote)
def main():
controller = QuoteTerminalController()
while True:
controller.run()
if __name__ == '__main__':
main()