I am getting TypeError : Postitional argument

Question

class learn:
    def __init__(self, first_name: str, last_name: str, age: int):
        self.first_name = first_name
        self.last_name = last_name
        self.age = age

    def __str__(self, acc):
        if isinstance(acc, learn):
            return f' My name is {self.first_name} {self.last_name} and I am {self.age}'
        raise Exception(f"{acc} is not of class learn ")


acc = learn('Ranjeet', 'Kumar', 22)
print(acc)

TypeError: __str__() missing 1 required positional argument: 'acc'

Answer 1

As described in the documentation, your custom __str__() method should only declare a single parameter, self that will always be of the type of your class, i.e. learn:

def __str__(self):
    return f' My name is {self.first_name} {self.last_name} and I am {self.age}'

# call via built-in functions str(acc) or print(acc)

Contrast this with a separate function that is detached from the class and could take any number of arguments:

def to_string(obj):
    if isinstance(obj, learn):
        return f' My name is {obj.first_name} {obj.last_name} and I am {obj.age}'
    raise Exception(f"{obj} is not of class learn ")

# call via to_string(acc)