What is a clean "pythonic" way to implement multiple constructors?
class, constructor, python
Solution
Actually `None` is much better for "magic" values:
class Cheese:
def __init__(self, num_holes=None):
if num_holes is None:
...
Now if you want complete freedom of adding more parameters:
class Cheese:
def __init__(self, *args, **kwargs):
# args -- tuple of anonymous arguments
# kwargs -- dictionary of named arguments
self.num_holes = kwargs.get('num_holes', random_holes())
To better explain the concept of `*args` and `**kwargs` (you can actually change these names):
def f(*args, **kwargs):
print('args:', args, 'kwargs:', kwargs)
>>> f('a')
args: ('a',) kwargs: {}
>>> f(ar='a')
args: () kwargs: {'ar': 'a'}
>>> f(1,2,param=3)
args: (1, 2) kwargs: {'param': 3}
http://docs.python.org/reference/expressions.html#calls
Problem
I can't find a definitive answer for this. As far as I know, you can't have multiple `__init__` functions in a Python class. So how do I solve this problem? Suppose I have a class called `Cheese` with the `number_of_holes` property. How can I have two ways of creating cheese objects... - One that takes a number of holes like this: `parmesan = Cheese(num_holes=15)`. - And one that takes no arguments and just randomizes the `number_of_holes` property: `gouda = Cheese()`. I can think of only one way to do this, but this seems clunky: ``` class Cheese: def __init__(self, num_holes=0): if num_holes == 0: # Randomize number_of_holes else: number_of_holes = num_holes ``` What do you say? Is there another way?