How do I avoid the “self.x = x; self.y = y; self.z = z” pattern in __init__?

Question

I see patterns like

def __init__(self, x, y, z):
    ...
    self.x = x
    self.y = y
    self.z = z
    ...

quite frequently, often with

Answer 1

This is a solution without any additional imports.

Helper function

A small helper function makes it more convenient and re-usable:

def auto_init(local_name_space):
    """Set instance attributes from arguments.
    """
    self = local_name_space.pop('self')
    for name, value in local_name_space.items():
        setattr(self, name, value)

Application

You need to call it with locals():

class A:
    def __init__(self, x, y, z):
        auto_init(locals())

Test

a = A(1, 2, 3)
print(a.__dict__)

Output:

{'y': 2, 'z': 3, 'x': 1}

Without changing locals()

If you don't like to change locals() use this version:

def auto_init(local_name_space):
    """Set instance attributes from arguments.
    """
    for name, value in local_name_space.items():
        if name != 'self': 
            setattr(local_name_space['self'], name, value)