TypeError: object() takes no parameters after defining __new__

Question

I really don't get where the error is in this little piece of code:

class Personne:     def __init__(self, nom, prenom):         print("Appel de la méthode __init__")         self.nom = nom         self.prenom = prenom      def __new__(cls, nom, prenom):         print("Appel de la méthode __new__ de la classe {}".format(cls))         return object.__new__(cls, nom, prenom)  personne = Personne("Doe", "John") 

It is giving me the error:

Traceback (most recent call last):   File "/home/bilal/Lien vers python/21_meta_classes/1_instanciation.py", line 21, in <module>     personne = Personne("Doe", "John")   File "/home/bilal/Lien vers python/21_meta_classes/1_instanciation.py", line 14, in __new__     return object.__new__(cls, nom, prenom) TypeError: object() takes no parameters 

Answer 1

In Python 3.3 and later, if you're overriding both __new__ and __init__, you need to avoid passing any extra arguments to the object methods you're overriding. If you only override one of those methods, it's allowed to pass extra arguments to the other one (since that usually happens without your help).

So, to fix your class, change the __new__ method like so:

def __new__(cls, nom, prenom):     print("Appel de la méthode __new__ de la classe {}".format(cls))     return object.__new__(cls) # don't pass extra arguments here!