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68
function_overloading/overload.py
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68
function_overloading/overload.py
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# https://www.codewars.com/kata/5f24315eff32c4002efcfc6a
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import inspect
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# https://docs.python.org/3.8/reference/datamodel.html#customizing-class-creation
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# https://snarky.ca/unravelling-pythons-classes/
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# https://gist.github.com/tmr232/c7214d62607ba1fc0e0a2e82d7e041cd
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class DispatchProxy:
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def __init__(self, name):
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self.registry = {}
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self.name = name
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def register(self, f):
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print(f"register {inspect.signature(f)}")
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argcount = f.__code__.co_argcount
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self.registry[argcount] = f
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"""
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def decorator(func):
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argcount = f.__code__.co_argcount
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self.registry[argcount] = f
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return func
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return decorator
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"""
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def __call__(self, *args):
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argcount = len(args) + 1 # add 1 because the first argument of a method is "self"
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if argcount in self.registry:
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resolved = self.registry[argcount]
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print(f"resolved: {resolved.__name__}{inspect.signature(resolved)}")
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return resolved(self, *args)
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else:
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raise AttributeError(f"No matching function for args: {args}")
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class MyNamespace(dict):
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def __getitem__(self, key):
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#(f"get {key}")
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return super().__getitem__(key)
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def __setitem__(self, key, value):
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#sign = inspect.signature(value) if callable(value) else value
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#print(f"set {key} {value}")
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# already exists => overload
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is_method = callable(value) and not value.__name__.startswith("__")
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if is_method and key in self:
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m = self[key]
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if not isinstance(m, DispatchProxy):
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m = DispatchProxy(self)
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m.register(self[key])
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m.register(value)
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super().__setitem__(key, m)
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else:
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super().__setitem__(key, value)
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class Meta(type):
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@classmethod
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def __prepare__(cls, name, bases):
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return MyNamespace()
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def __new__(cls, name, bases, dct):
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x = super().__new__(cls, name, bases, dct)
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return x
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def __init__(self, name, bases, attrs):
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super(Meta, self).__init__(name, bases, attrs)
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160
function_overloading/tests.py
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function_overloading/tests.py
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import codewars_test as test
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from overload import Meta
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cng_msg = 'Dont change the properties of class.'
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sld_work = 'Function overloading should work.'
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@test.describe('Python Recipes #1 : Function Overloading')
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def _():
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# implement meta class -----
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def build(): # returning class to regenerate accordingly.
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class Overload(metaclass=Meta):
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CLS_VAR = 42
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def __init__(self):
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self.a = 1
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self.no = 'This is "No parameter" function.'
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self.single = 'This is "Single parameter" function'
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self.two = 'This is "Two parameter" function'
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self.three = 'This is "Three parameter" function'
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def foo(self):
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return self.no
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def foo(self, x):
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return self.single + ':' + str(x)
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def foo(self, x, y):
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return self.two + ':' + str(x) + ',' + str(y)
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def foo(self, x, y, z):
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return self.three + ':' + str(x) + ',' + str(y) + ',' + str(z)
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def extra(self):
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return 'This is extra method.'
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return Overload
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@test.describe('Sample tests')
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def _():
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overload = build()
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obj = overload()
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@test.it('Verifying access')
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def _():
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test.assert_equals(obj.a, 1, cng_msg)
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test.assert_equals(obj.no, 'This is "No parameter" function.', cng_msg)
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test.assert_equals(obj.single, 'This is "Single parameter" function', cng_msg)
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test.assert_equals(obj.two, 'This is "Two parameter" function', cng_msg)
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test.assert_equals(obj.three, 'This is "Three parameter" function', cng_msg)
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test.assert_equals(obj.extra(), 'This is extra method.', cng_msg)
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test.assert_equals(obj.CLS_VAR, 42, cng_msg)
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@test.it('Verifying overloading feature')
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def _():
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test.assert_equals(obj.foo(), 'This is "No parameter" function.', sld_work)
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test.assert_equals(obj.foo(1), 'This is "Single parameter" function:1', sld_work)
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test.assert_equals(obj.foo(1,2), 'This is "Two parameter" function:1,2', sld_work)
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test.assert_equals(obj.foo(1,2,3), 'This is "Three parameter" function:1,2,3', sld_work)
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@test.it('Verifying overloading feature after adding new methods :1')
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def _():
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def foo(self, a, b, c, d):
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return self.a + a + b + c + d
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def foo1(self, a, b):
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return 'Overwritten'
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overload.foo = foo
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test.assert_equals(obj.foo(), 'This is "No parameter" function.', sld_work)
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test.assert_equals(obj.foo(1), 'This is "Single parameter" function:1', sld_work)
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test.assert_equals(obj.foo(1,2), 'This is "Two parameter" function:1,2', sld_work)
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test.assert_equals(obj.foo(1,2,3), 'This is "Three parameter" function:1,2,3', sld_work)
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test.assert_equals(obj.foo(1,2,3,4), 11, sld_work)
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overload.foo = foo1
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test.assert_equals(obj.foo(1,2), 'Overwritten', sld_work)
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@test.it('Verifying overloading feature after adding new methods :2')
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def _():
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def boo1(self):
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return self.a
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def boo2(self, a):
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return self.a + a
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def unique(self, a, b):
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return a + b
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overload.boo = boo1
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overload.boo = boo2
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obj.nothing = '123'
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overload.unique = unique
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test.assert_equals(obj.boo(), 1, sld_work)
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test.assert_equals(obj.boo(1), 2, sld_work)
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test.assert_equals(obj.unique(1, 2), 3, sld_work)
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test.assert_equals(obj.nothing, '123', sld_work)
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@test.describe('Verify the absence of unwanted sharing of methods between different classes')
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def _():
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class Unshare(metaclass=Meta):
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def foo(self,a,b): return 'unshared!'
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unsh=Unshare()
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@test.it('The new foo function in Unshare class should be used')
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def _():
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test.assert_equals(unsh.foo(1,2), 'unshared!')
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@test.it('Previous implementations of "foo" in other classes shouldn\'t be visible from a freshly built class')
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def _():
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test.expect_error("Your function didn't raise any exception", lambda: unsh.foo(1), Exception)
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test.expect_error("Your function should raise AttributeError", lambda: unsh.foo(1), AttributeError)
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@test.it('Previous method with the same signature in other classes shouldn\'t be affected')
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def _():
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test.assert_equals(obj.foo(1,2), 'Overwritten')
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@test.it('Class level variables are still working as expected')
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def _():
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def over(): obj.CLS_VAR=-42
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def write(): obj.HAHA=msg
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test.expect_no_error("Class level variables can be overriden", over)
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test.assert_equals(obj.CLS_VAR, -42, "Class variable Overload.CLS_VAR hasn't been overriden")
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msg = 'This is another class variable'
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test.expect_no_error("New class level variables can be defined", write)
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test.assert_equals(obj.HAHA, msg, "New class level variables can be defined and accessed")
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@test.it('Undefined methods or variables should raise AttributeError')
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def _():
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test.expect_error('Undefined attributes/mehtods should raise AttributeError',
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lambda: overload.NEW_CLS_VAR, AttributeError)
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test.expect_error('Undefined attributes/mehtods should raise AttributeError',
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lambda: obj.ABCD, AttributeError)
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test.expect_error('Undefined attributes/mehtods should raise AttributeError',
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lambda: obj.randomFuncName(), AttributeError)
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@test.it('undefined overloaded methods (wrong number of arguments should raise AttributeError)')
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def _():
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test.expect_error('Undefined attributes/mehtods should raise AttributeError',
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lambda: overload.foo(1,1,1,1,1,1,1,1,1,1,1,1,1,1,1), AttributeError)
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