如何在 Python 中重新定义实例方法？

Question

我正在为方法 dbg（代表 debug_message）、info（代表 info_message）以及 log（日志记录功能）构建基础设施。

无论用户输入什么，dbg、info 和 log 方法都会被调用，但是，它们的功能会根据用户输入而有所不同，例如用户是否希望进程打印 DEBUG 或完全安静，以及用户是否想要记录。

只要我不使用对象来包装功能（出于多重原因），我就可以实现这样的功能。 当我将它包装成一个对象并从一个对象调用它时，我得到AttributeError ，该对象没有方法。

class Feedbacker(object):
    def __init__(self, task):
        self.LOG = task.LOG
        self.LOG_DIR = task.LOG_DIR
        self.DEBUG = task.DEBUG
        self.QUIET = task.QUIET

        self.timestamp = datetime.now().strftime("%Y-%m-%d_%H%M%S")

        # Logging
        # Based on parameter input. Creates a log file and logs all info output.
        if self.LOG: # If logging parameter was provided -> Initiate logging
            Path(self.LOG_DIR).mkdir(parents=True, exist_ok=True) # Creates directory

            import logging
            logging.basicConfig(format='%(asctime)s %(message)s',\
                handlers=[logging.FileHandler(\
                f"{self.LOG_DIR}/ytr_log_{self.timestamp}.log", 'w', 'utf-8')]) # UTC-8
            logging.logThreads = 0
            logging.logProcesses = 0
            logger=logging.getLogger()
            logger.setLevel(logging.ERROR)
            def log(*args,**kwargs):
                msg = " ".join(args) # Joins all args into one string. " " seperator.
                logger.log(60, msg) # First agr is the log level.

        else: # If logging is not provided, log will still be run, but will do nothing.
            def log(*args,**kwargs):
                pass
        # Debug message handling
        if self.DEBUG:
            def dbg(*args, head = "DEBUG", **kwargs):
                info(*args, head = head, **kwargs)
        else:
            def dbg(self, *args, head = "DEBUG", **kwargs):
                log(f"[{head}]: ", *args, **kwargs)
                pass
        # Quiet execution
        if self.QUIET:
            def info(*args, head = "INFO", **kwargs):
                log(f"[{head}]: ", *args,**kwargs)
        else:
            def info(*args, head = "INFO", **kwargs):
                print(f"[{head}]: ", *args,**kwargs)
                log(f"[{head}]: ", *args,**kwargs)

# Example call, which does not work.
fb = Feedbacker(task)
fb.dbg("Test message")

如何基于实例变量定义 dbg 方法？

Answer 1

函数是python中的值，因此您可以任意重新分配它们。

您可以执行以下操作（简化示例）：

class Feedbacker(object):
    def __init__(self, switch):
        if switch:
            self.foo = self.bar

    def foo(*args):
        return "something"

    def bar(*args):
        return "something_different"

print(Feedbacker(False).foo()) # something
print(Feedbacker(True).foo()) # something_different

Answer 2

我认为，对您所拥有的内容进行重新编辑（有限测试）。 我不得不做一个虚拟的任务定义，它肯定与你原来的不同：

from datetime import datetime
from pathlib import Path

class Task:
    LOG = True
    LOG_DIR = 'C:\Temp\Logs'
    DEBUG = True
    QUIET = True

task = Task()

class Feedbacker(object):
    def __init__(self, task):
        self.LOG = task.LOG
        self.LOG_DIR = task.LOG_DIR
        self.DEBUG = task.DEBUG
        self.QUIET = task.QUIET

        self.timestamp = datetime.now().strftime("%Y-%m-%d_%H%M%S")

        # Logging
        # Based on parameter input. Creates a log file and logs all info output.
        if self.LOG: # If logging parameter was provided -> Initiate logging
            Path(self.LOG_DIR).mkdir(parents=True, exist_ok=True) # Creates directory

            import logging
            logging.basicConfig(format='%(asctime)s %(message)s',\
                handlers=[logging.FileHandler(\
                f"{self.LOG_DIR}/ytr_log_{self.timestamp}.log", 'w', 'utf-8')]) # UTC-8
            logging.logThreads = 0
            logging.logProcesses = 0
            self.logger=logging.getLogger()
            self.logger.setLevel(logging.ERROR)
            self.log = self.log_a

        else: # If logging is not provided, log will still be run, but will do nothing.
            self.log = self.log_b

        # Debug message handling
        if self.DEBUG:
            self.dbg = self.dbg_a
        else:
            self.dbg = self.dbg_b

        # Quiet execution
        if self.QUIET:
            self.info = self.info_a
        else:
            self.info = self.info_b

    def log_a(self,*args,**kwargs):
        msg = " ".join(args) # Joins all args into one string. " " seperator.
        self.logger.log(60, msg) # First agr is the log level.

    def log_b(self,*args,**kwargs):
        pass

    def dbg_a(self,*args, head = "DEBUG", **kwargs):
        self.info(*args, head = head, **kwargs)

    def dbg_b(self, *args, head = "DEBUG", **kwargs):
        self.log(f"[{head}]: ", *args, **kwargs)

    def info_a(self,*args, head = "INFO", **kwargs):
        self.log(f"[{head}]: ", *args,**kwargs)

    def info_b(self,*args, head = "INFO", **kwargs):
        print(f"[{head}]: ", *args,**kwargs)
        self.log(f"[{head}]: ", *args,**kwargs)

# Create the logging object and output test message
fb = Feedbacker(task)
fb.dbg("Test message")

阅读您的评论后，您会发现在各种调用中检查您的配置变量要简洁得多：

class Feedbacker(object):
    def __init__(self, task):
        self.LOG = task.LOG
        self.LOG_DIR = task.LOG_DIR
        self.DEBUG = task.DEBUG
        self.QUIET = task.QUIET

        self.timestamp = datetime.now().strftime("%Y-%m-%d_%H%M%S")

        # Logging
        # Based on parameter input. Creates a log file and logs all info output.
        if self.LOG: # If logging parameter was provided -> Initiate logging
            Path(self.LOG_DIR).mkdir(parents=True, exist_ok=True) # Creates directory

            import logging
            logging.basicConfig(format='%(asctime)s %(message)s',
                handlers=[logging.FileHandler(
                f"{self.LOG_DIR}/ytr_log_{self.timestamp}.log", 'w', 'utf-8')]) # UTC-8
            logging.logThreads = 0
            logging.logProcesses = 0
            self.logger=logging.getLogger()
            self.logger.setLevel(logging.ERROR)

    def log(self,*args,**kwargs):
        if self.LOG:
            msg = " ".join(args) # Joins all args into one string. " " seperator.
            self.logger.log(60, msg) # First agr is the log level.

    def dbg(self,*args, head = "DEBUG", **kwargs):
        if self.DEBUG:
            self.info(*args, head = head, **kwargs)
        else:
            self.log(f"[{head}]: ", *args, **kwargs)

    def info(self,*args, head = "INFO", **kwargs):
        if not self.QUIET:
            print(f"[{head}]: ", *args,**kwargs)
        self.log(f"[{head}]: ", *args,**kwargs)

# Sample call
fb = Feedbacker(task)

fb.dbg("Test message")