Initial commit

Solutions/6_5/validate.py

@@ -0,0 +1,109 @@
+class Validator:
+    def __init__(self, name=None):
+        self.name = name
+
+    def __set_name__(self, cls, name):
+        self.name = name
+
+    @classmethod
+    def check(cls, value):
+        return value
+
+    def __set__(self, instance, value):
+        instance.__dict__[self.name] = self.check(value)
+
+class Typed(Validator):
+    expected_type = object
+    @classmethod
+    def check(cls, value):
+        if not isinstance(value, cls.expected_type):
+            raise TypeError(f'expected {cls.expected_type}')
+        return super().check(value)
+
+class Integer(Typed):
+    expected_type = int
+
+class Float(Typed):
+    expected_type = float
+
+class String(Typed):
+    expected_type = str
+
+class Positive(Validator):
+    @classmethod
+    def check(cls, value):
+        if value < 0:
+            raise ValueError('must be >= 0')
+        return super().check(value)
+
+class NonEmpty(Validator):
+    @classmethod
+    def check(cls, value):
+        if len(value) == 0:
+            raise ValueError('must be non-empty')
+        return super().check(value)
+
+class PositiveInteger(Integer, Positive):
+    pass
+
+class PositiveFloat(Float, Positive):
+    pass
+
+class NonEmptyString(String, NonEmpty):
+    pass
+
+from inspect import signature
+
+class ValidatedFunction:
+    def __init__(self, func):
+        self.func = func
+        self.signature = signature(func)
+        self.annotations = dict(func.__annotations__)
+        self.retcheck = self.annotations.pop('return', None)
+
+    def __call__(self, *args, **kwargs):
+        bound = self.signature.bind(*args, **kwargs)
+
+        for name, val in self.annotations.items():
+            val.check(bound.arguments[name])
+
+        result = self.func(*args, **kwargs)
+
+        if self.retcheck:
+            self.retcheck.check(result)
+
+        return result
+
+# Examples
+if __name__ == '__main__':
+    def add(x:Integer, y:Integer) -> Integer:
+        return x + y
+
+    add = ValidatedFunction(add)
+
+    class Stock:
+        name = NonEmptyString()
+        shares = PositiveInteger()
+        price = PositiveFloat()
+        def __init__(self, name, shares, price):
+            self.name = name
+            self.shares = shares
+            self.price = price
+
+        def __repr__(self):
+            return f'Stock({self.name!r}, {self.shares!r}, {self.price!r})'
+
+        @property
+        def cost(self):
+            return self.shares * self.price
+
+        def sell(self, nshares):
+            self.shares -= nshares
+
+        sell = ValidatedFunction(sell)     # Broken
+
+
+
+    
+
+