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python - 从另一个类修改一个类的功能

问题描述

在server.sync的 pymodbus 库中，使用了SocketServer.BaseRequestHandler，定义如下：

class ModbusBaseRequestHandler(socketserver.BaseRequestHandler):
""" Implements the modbus server protocol
This uses the socketserver.BaseRequestHandler to implement
the client handler.
"""
running = False
framer = None

def setup(self):
    """ Callback for when a client connects
    """
    _logger.debug("Client Connected [%s:%s]" % self.client_address)
    self.running = True
    self.framer = self.server.framer(self.server.decoder, client=None)
    self.server.threads.append(self)

def finish(self):
    """ Callback for when a client disconnects
    """
    _logger.debug("Client Disconnected [%s:%s]" % self.client_address)
    self.server.threads.remove(self)

def execute(self, request):
    """ The callback to call with the resulting message
    :param request: The decoded request message
    """
    try:
        context = self.server.context[request.unit_id]
        response = request.execute(context)
    except NoSuchSlaveException as ex:
        _logger.debug("requested slave does not exist: %s" % request.unit_id )
        if self.server.ignore_missing_slaves:
            return  # the client will simply timeout waiting for a response
        response = request.doException(merror.GatewayNoResponse)
    except Exception as ex:
        _logger.debug("Datastore unable to fulfill request: %s; %s", ex, traceback.format_exc() )
        response = request.doException(merror.SlaveFailure)
    response.transaction_id = request.transaction_id
    response.unit_id = request.unit_id
    self.send(response)

# ----------------------------------------------------------------------- #
# Base class implementations
# ----------------------------------------------------------------------- #
def handle(self):
    """ Callback when we receive any data
    """
    raise NotImplementedException("Method not implemented by derived class")

def send(self, message):
    """ Send a request (string) to the network
    :param message: The unencoded modbus response
    """

raise NotImplementedException("方法未由派生类实现")

当客户端连接到服务器时调用 setup()，当客户端断开连接时调用 finish()。我想在另一个使用库（pymodbus）的文件的另一个类中操作这些方法（setup（）和finish（）），并添加一些代码来设置和完成函数。我不打算修改库，因为它可能会在特定情况下导致奇怪的行为。

---已编辑----为了澄清，我希望 ModbusBaseRequestHandler 类中的设置函数像以前一样工作并且保持不变，但是添加其他东西，但是这个修改应该在我的代码中而不是在库中完成。

标签： pythonhandlersocketserverpymodbus

解决方案

它可以通过拦截器完成

from functools import wraps 

def iterceptor(func):
    print('this is executed at function definition time (def my_func)')

@wraps(func)
def wrapper(*args, **kwargs):
    print('this is executed before function call')
    result = func(*args, **kwargs)
    print('this is executed after function call')
    return result

return wrapper


@iterceptor
def my_func(n):
   print('this is my_func')
   print('n =', n)


my_func(4)

更多解释可以在这里找到

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