My admittedly rudimentary understanding of decorators is that they should add functionality without changing the function's syntax. But how does one handle the case when one wants a wrapper that uses arguments not processed by the main function. For instance, I have a bunch of functions that process text from a file. To avoid having to open or close the files I want to use a decorator that (1) imports the files, (2) passes the lines to the text handler and (3) saves the file. Assuming that lines contains the contents of the file file.abc, I came up with the following: def readwrite(func): def inner(*args, **kwargs): if 'file' not in kwargs.keys(): print("Opening", args[0]) lines = "lorem ipsum and all that" #Assume file returns this content. else: print("Reading", kwargs['file']) lines = 'lorem ipsum and all that' func(*args, **kwargs) print("Closing file") return return inner @readwrite def remove_lipsum(lines): print("Removing ipsum from ", lines) return remove_lipsum('file.abc') This returns: Opening file.abc Removing ipsum from file.abc Closing file The if-else comes because the file might be passed as a name or unnamed argument. The problem of course is that now I have the wrapper accepting an argument not in the function definition. What would be the correct way to go about it? Simply use nested loops instead of decorators? Continue reading...
