Python Factory Method Suggestions

Question

I would like to ask you to help me out with my factory method. I have to handle multiple and periodic csv objects, each of which has its own properties, thus its own class. The only way I can tell Python one csv differs from another, is due to the file name. Now, I create different object based on the file name, as follows:

class CSVFileFactory: @staticmethod def obj_builder(fname: str): if "type1" in fname: return TypeOneCSV(filename=fname) elif "type2" in fname: return TypeTwoCSV(filename=fname) elif "type3" in fname: return TypeThreeCSV(filename=fname) ... ...

And so on. Do you think this is the cleanest way I could do it? Are there any conventions I'm not applying? Do you have any suggestion to reduce code complexity and the never-ending "if-elif" statement? Thanks a lot for the help!

class CSVFileFactory: no. Python is not Java. This should just be a function. A class with a single staticmethod should just be a function — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Dec 23, 2022 at 9:02
In any case, there is nothing really wrong with your if...elif. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Dec 23, 2022 at 9:03
You could maybe try to extract the type with a regex and use a dict instead, but I don't think that really gives you much of an advantage — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Dec 23, 2022 at 9:09
Thank you! I'm not used to factory methods and that is what I found online, I just thought it was the "right way to do it". Thanks again! — Marco
– Marco, Commented Dec 23, 2022 at 9:15

Homer512 · Accepted Answer · 2022-12-23 09:18:19Z

As suggested, a class is not necessary, especially when you just use a static method (BTW: Spelling error in the decorator). If you want a namespace, create a module for it, otherwise just use a function.

For the code itself, you can make a loop if the construction follows the exact same pattern. Might be a bit shorter.

def open_csv_file(fname: str): filetypes = (("type1", TypeOneCSV), ("type2", TypeTwoCSV), ("type3", TypeThreeCSV), ) for pattern, classtype in filetypes: if pattern in fname: return classtype(filename=fname) raise ValueError("unknown file type")

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