当我调用内部/装饰函数时，我可以将参数传递给我的装饰器函数吗？

Question

Hopefully that terminology is correct. I have this decorator function, which reads a text file:

def read_commands(inner, path=BATCH_PATH):
    with open(path) as f:
        commands = ['python ' + line.replace('\n', '') for line in f]

    def wrapper(*args, **kwargs):
        for command in commands:
            inner(command, *args, **kwargs)

    return wrapper

And here's one of the functions it decorates:

@read_commands
def execute_multi_commands(command, count):
    LOG.info(f'Executing command {count}: {command}')
    os.system(command)
    count += 1

I want to be able to change path from default when I call execute_multi_commands , like so in my main :

def main():
    parser = argparse.ArgumentParser()

    parser.add_argument('-b', '--batch', action='store', type=str, dest='batch')
    args = parser.parse_args()
    
    count = 1
    execute_multi_commands(count, path=args.batch)

However, obviously this does not work as path is not an argument in execute_multi_commands . Is it possible for me to pass path to the decorator function read_commands , when I call execute_multi_commands ? - or, more likely, any functionally equivalent alternatives?

Answer 1

You cannot, at least the way your decorator is written. When you decorate a function, it's similar to doing:

def execute_multi_commands(command, count):
    LOG.info(f'Executing command {count}: {command}')
    os.system(command)
    count += 1

execute_multi_commands = read_commands(execute_multi_commands)

So after this point, read_commands has already been executed, and the file has been read.

What you can do is change the decorator to read the file in the wrapper, something like:

def read_commands(inner, path=BATCH_PATH):

    def wrapper(*args, **kwargs):

        if "path" in kwargs:
            path_ = kwargs.pop("path")
        else:
            path_ = path

        with open(path_) as f:
            commands = ['python ' + line.replace('\n', '') for line in f]

        for command in commands:
            inner(command, *args, **kwargs)

    return wrapper

...but this means reading the file every time you call the decorated function, which is slightly different than what you were doing before.