Python function with a lot of arguments

Question

I am new to Python and higher level languages in general, so I was wondering if it is looked down upon if I have a function that takes in a lot of arguments, and how to better architect my code to prevent this.

For example what this function is essentially doing is printing each location of a string in a file.

def scan(fpin,base,string,pNo,print_to_file,dumpfile_path,quiet):

This function is being called from the main function, which is basically parsing the command line arguments and passing the data to the scan function. I have thought of creating a class containing all of these arguments and passing it to scan,but there will only be one instance of this data, so wouldn't that be pointless?

Answer 1

Named arguments are your friends. For things that act like semi-optional configuration options with reasonable defaults, give the parameters the defaults, and only pass them (as named arguments) for non-default situations. If there are a lot of parameters without reasonable defaults, then you may want to name all of them when you call the function.

Consider the built-in function sorted. It takes up to four arguments. Is the reverse parameter before or after cmp? What should I pass in as key if I want the default behavor? Answer: Hell if I can remember. I call sorted(A, reverse=True) and it does what I'd expect.

Incidentally, if I had a ton of "config"-style arguments that I was passing into every call to scan, and only changing (say, fpin and string) each time, I might be inclined to put all the other argumentsinto a dictionary, and then pass it to the function with **kwargs syntax. That's a little more advanced. See the manual for details. (Note that this is NOT the same as declaring the function as taking **kwargs. The function definition is the same, the only difference is what calls to it look like.)