lisa.utils.PartialInit

class lisa.utils.PartialInit(*args, **kwargs)

Bases: object

Allow partial initialization of instances with curry-like behaviour for the constructor.

Subclasses will be able to be used in this way:

class Sub(PartialInit):
    def __init__(self, x, y):
        self.x = x
        self.y = y

    # This decorator allows the classmethod to be partially applied as
    # well.
    #
    # Note: since PartialInit relies on accurate signatures, **kwargs
    # cannot be used, unless the signature is patched-up with something
    # like lisa.utils.kwargs_forwarded_to()
    @PartialInit.factory
    def factory(cls, x, y):
        return cls(x=x, y=y)


# Bind x=1
# Sub.__init__ not yet called
obj = Sub(1)

# Provide a value for "y", which will trigger a call to the
# user-provided __init__
obj = obj(y=2)

# Make a new instance with value of x=42, and all the other parameters
# being the same as what was provided to build "obj"
obj2 = obj(x=42)

Note

any attribute access on a partially initialized instance will result in a TypeError exception.

Methods

factory()

Decorator to use on alternative constructors, i.e. classmethods that return instances of the class.

Methods

classmethod PartialInit.factory(f)

Decorator to use on alternative constructors, i.e. classmethods that return instances of the class.

Once decorated, the classmethod can be partially applied just like the class itself.

Note

@classmethod is applied automatically if not already done by the user.