python - 装饰后不再获取函数的返回值

Question

在Python 101一书中，第162页，有一个关于日志装饰器函数的示例。代码如下:

import logging

def log(func):
   """
   Log what function is called
   """
   def wrap_log(*args, **kwargs):
      name = func.__name__
      logger = logging.getLogger(name)
      logger.setLevel(logging.INFO)

      # add file handler
      fh = logging.FileHandler("%s.log" % name)
      fmt = '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
      formatter = logging.Formatter(fmt)
      fh.setFormatter(formatter)
      logger.addHandler(fh)

      logger.info("Running function: %s" % name)
      result = func(*args, **kwargs)
      logger.info("Result: %s" % result)
      return func
   return wrap_log

@log
def double_function(a):
   """
   Double the input parameter
   """
   return a*2

if __name__=="__main__":
   value = double_function(2)

通常，value代码末尾应等于 double_function 的返回值，在本例中等于 4。然而执行后在控制台查看，发现等于double_function它本身，而不是它的返回值(是的，value 成为了函数)。

为什么会发生这种情况？我该如何使用 double_function作为返回其正确返回值的普通函数？

注意:我使用的是 Python 3.6.5。

Answer 1

@aran-fey 是对的

import logging

def log(func):
   """
   Log what function is called
   """
   def wrap_log(*args, **kwargs):
      name = func.__name__
      logger = logging.getLogger(name)
      logger.setLevel(logging.INFO)

      # add file handler
      fh = logging.FileHandler("%s.log" % name)
      fmt = '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
      formatter = logging.Formatter(fmt)
      fh.setFormatter(formatter)
      logger.addHandler(fh)

      logger.info("Running function: %s" % name)
      result = func(*args, **kwargs)
      logger.info("Result: %s" % result)
      return result  # Your error was you returned the function, not the result
   return wrap_log

@log
def double_function(a):
   """
   Double the input parameter
   """
   return a*2

if __name__=="__main__":
   value = double_function(2)
   print(value)