How to define an instance depending on some variable? - oop

Question

I'll give code on Python, but it's doesn't matter.
I have a module argument_parser with dictionary and class:
FORMATS = {
'JSON': 'json',
'XML': 'xml',
}
class ArgumentParser:
# some methods
def parse():
"""returns 'XML' or 'JSON' string"""
return fomat
and a module with presenters -- presenter
class JSONPresenter:
# some magic
class XMLPresenter:
# some magic
The problem is in dependency injection:
argument_parser = ArgumentParser()
format = argument_parser.parse()
if format == argument_parser.FORMATS['JSON']:
presenter = JSONFilePresenter()
elif format == argument_parser.FORMATS['XML']:
presenter = XMLFilePresenter()
if-elif construction is ugly. If I want to add some other formats I'll must add more elif.
I could define the type of presenter in ArgumentParser class but I think semantically it is wrong -- it is not a filed of responsibility of this class. What should I do to do it right?

Answer 1

PRESENTERS = {
'json': JSONPresenter(),
'xml': XMLPresenter(),
}
argument_parser = ArgumentParser()
fmt = argument_parser.parse()
presenter = PRESENTERS[fmt]
Or, if you need a new presenter every time:
PRESENTERS = {
'json': lambda: JSONPresenter(),
'xml': lambda: XMLPresenter(),
}
argument_parser = ArgumentParser()
fmt = argument_parser.parse()
presenter = PRESENTERS[fmt]()