[Python] python recursion error, calling classmethod of derived class in __new__ method

I have the following piece of code - simplified version of what I want to do. But it gives me a recursion error.

class File:
def __new__(cls, filename):
extension = filename.split(".")[-1].lower()

if extension == "csv":
cls = CSVFile
elif extension == "json":
cls = JSONFile
else:
raise ValueError(f"Unsupported file extension: {extension}")

# instance = super().__new__(cls) # this works
instance = cls.create_instance(filename)
return instance

class CSVFile(File):
def __init__(self, filename):
self.filename = filename

@classmethod
def create_instance(cls, filename):
print("CSVFile, create_instance")
return cls(filename)

class JSONFile(File):
def __init__(self, filename):
self.filename = filename

@classmethod
def create_instance(cls, filename):
print("JSONFile, create_instance")
return cls(filename)

# Example usage
file_instance = File("data.csv")
print(f"File instance: {file_instance.filename}")


Do you have idea how to make it work?

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