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from multipledispatch.utils import typename
class VariadicSignatureType(type):
# checking if subclass is a subclass of self
def __subclasscheck__(self, subclass):
other_type = subclass.variadic_type if isvariadic(subclass) else (subclass,)
return subclass is self or all(
issubclass(other, self.variadic_type) for other in other_type
)
def __eq__(self, other):
"""
Return True if other has the same variadic type
Parameters
----------
other : object (type)
The object (type) to check
Returns
-------
bool
Whether or not `other` is equal to `self`
"""
return isvariadic(other) and set(self.variadic_type) == set(other.variadic_type)
def __hash__(self):
return hash((type(self), frozenset(self.variadic_type)))
def isvariadic(obj):
"""Check whether the type `obj` is variadic.
Parameters
----------
obj : type
The type to check
Returns
-------
bool
Whether or not `obj` is variadic
Examples
--------
>>> isvariadic(int)
False
>>> isvariadic(Variadic[int])
True
"""
return isinstance(obj, VariadicSignatureType)
class VariadicSignatureMeta(type):
"""A metaclass that overrides ``__getitem__`` on the class. This is used to
generate a new type for Variadic signatures. See the Variadic class for
examples of how this behaves.
"""
def __getitem__(self, variadic_type):
if not (isinstance(variadic_type, (type, tuple)) or type(variadic_type)):
raise ValueError(
"Variadic types must be type or tuple of types"
" (Variadic[int] or Variadic[(int, float)]"
)
if not isinstance(variadic_type, tuple):
variadic_type = (variadic_type,)
return VariadicSignatureType(
"Variadic[%s]" % typename(variadic_type),
(),
dict(variadic_type=variadic_type, __slots__=()),
)
class Variadic(metaclass=VariadicSignatureMeta):
"""A class whose getitem method can be used to generate a new type
representing a specific variadic signature.
Examples
--------
>>> Variadic[int] # any number of int arguments
<class 'multipledispatch.variadic.Variadic[int]'>
>>> Variadic[(int, str)] # any number of one of int or str arguments
<class 'multipledispatch.variadic.Variadic[(int, str)]'>
>>> issubclass(int, Variadic[int])
True
>>> issubclass(int, Variadic[(int, str)])
True
>>> issubclass(str, Variadic[(int, str)])
True
>>> issubclass(float, Variadic[(int, str)])
False
"""
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