Provide a way to have attributes that have an inital value, but no keyword argument.

[tomprince]

Given that attrs doesn't allow composing with a custom __init__, there is no way to initialize mutable implementation details.

For example,

class Pool(object):
   def __init__(self, pool_size):
       self.pool_size = pool_size
       self._pool = []
    ...

can't be expressed with attrs.

[hynek]

_pool = attr.ib(default=attr.Factory(list)) is what I use.

Maybe I could support init=False such that it’s actually impossible to pass values for it? In my internal software I don’t care and just don’t pass anything, but if you’re building public APIs I see the value.

OTOH, I have written custom __init__s before. In the end it’s more readable than giving 1000s of options and variations to hit every single edge-case.

[hynek]

Is #32 an adequate solution to your problem?

[tomprince]

It looks like it is.