Python - decorator運用(1)

在trace程式碼的時候，尤其是多執行緒的程式碼，想知道函式的呼叫情況，此時會記錄函式的進出資訊。在python，可以使用decorator幫助記錄。

import functools
import time

def logFunc(logger = None):
   
    def log_decorator(function):
       
        @functools.wraps(function)
        def decorator_wrapper(*args, **kwargs):
            if logger is None:
                print("{2} [Debug] Enter {0}.{1}".format(function.__module__, function.__name__, time.asctime()))
                result = function(*args, **kwargs)
                print("{2} [Debug] Exit {0}.{1}".format(function.__module__, function.__name__, time.asctime()))
            else:
                logger.debug("Enter {0}.{1}".format(function.__module__, function.__name__))
                result = function(*args, **kwargs)
                logger.debug("Exit {0}.{1}".format(function.__module__, function.__name__))
            return result
       
        return decorator_wrapper
   
    return log_decorator

另外，有時需要記錄函式的執行時間，一樣可以使用decorator幫助記錄。

import functools
import time

def logTime(logger = None):
   
    def time_decorator(function):
       
        def decorator_wrapper(*args, **kwargs):
            start = time.time()
            result = function(*args, **kwargs)
            end = time.time()
            if logger is None:
                print("{3} [Debug] {0}.{1} spent {2:.3f} seconds.".format(function.__module__, function.__name__, end - start, time.asctime()))
            else:
                logger.debug("{0}.{1} spent {2:.3f} seconds.".format(function.__module__, function.__name__, end - start))
            return result
       
        return decorator_wrapper
   
    return time_decorator

在這裡的logger是指logging.logger。

decorator的使用方式為：

@logFunc(logger)
def foo1():
  # expressions

@logTime(logger)
def foo2():
  # expressions