class methods

‘Java · ‘Java · commit 47f2cee7ccc1 · 2024-08-29T07:14:09.000+05:30
diff --git a/code_with_closures.py b/code_with_closures.py
@@ -0,0 +1,34 @@
+def typed_property(name, expected_type):
+    private_name = '_' + name
+
+    @property
+    def prop(self):
+        return getattr(self, private_name)
+
+    @prop.setter
+    def prop(self, value):
+        if not isinstance(value, expected_type):
+            raise TypeError(f'Expected {expected_type}')
+        setattr(self, private_name, value)
+
+    return prop
+
+
+Integer = lambda name: typed_property(name, int)
+Float = lambda name: typed_property(name, float)
+
+
+class Holdings:
+    shares = Integer('shares')
+    prices = Float('prices')
+
+    def __init__(self, name, shares, prices):
+        self.name = name
+        self.shares = shares
+        self.prices = prices
+
+
+if __name__ == '__main__':
+    h = Holdings('IBM', 25, 4.1)
+    print(f'{h.name} cost : {h.shares * h.prices}')
+    # h.shares = '10'  # TypeError: Expected <class 'int'>
diff --git a/container_obj.py b/container_obj.py
@@ -0,0 +1,67 @@
+
+class Holding:
+    def __init__(self, name, shares, price, date):
+        self.name = name
+        self.shares = shares
+        self.price = price
+        self.date = date
+
+    def cost(self):
+        return self.price * self.shares
+
+    def sell(self, nshares):
+        self.shares -= nshares
+
+    @classmethod
+    def print_table(cls, objects, col_names):
+        print(f'Found {len(objects)} records')
+        for col_name in col_names:
+            print('{:>10s}'.format(col_name), end=' ')
+        print()
+
+        for obj in objects:
+            for col_name in col_names:
+                print('{:>10s}'.format(str(getattr(obj, col_name))), end=' ')
+            print()
+
+
+class Portfolio:
+
+    def __init__(self):
+        self.holdings = []
+
+    @classmethod
+    def load(cls):
+        self = cls()
+        self.holdings.append(Holding('AA', 23, 45.6, '2023-07-08'))
+        self.holdings.append(Holding('IBM', 75, 34.6, '2023-06-08'))
+        self.holdings.append(Holding('IBM', 15, 300.6, '2023-05-01'))
+        self.holdings.append(Holding('MSFT', 15, 151.6, '2023-07-08'))
+        return self
+
+    def __iter__(self):
+        return self.holdings.__iter__()
+
+    def __len__(self):
+        return self.holdings.__len__()
+
+    def __getattr__(self, item):
+        # holdings.append and list related function exposed
+        return getattr(self.holdings, item)
+
+
+if __name__ == '__main__':
+    h = Holding('AA', 23, 45.6, '2023-07-08')
+    print('Class attribute read h.name ', h.name)
+    h.name = 'Modified'
+    print('Class attribute set h.name ', h.name)
+    # del h.name
+    # AttributeError: 'Holding' object has no attribute 'name'
+    # print('Class attribute delete h.name ', h.name)
+
+    holdings = Portfolio.load()
+
+    print(holdings.append)
+
+    Holding.print_table(holdings, ['name', 'price'])
+
diff --git a/context_manager.py b/context_manager.py
@@ -0,0 +1,19 @@
+def __enter__(self):
+    print('Entering')
+    return 'some data'
+class Manager:
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        print('Existing')
+        print(exc_type, exc_val, exc_tb)
+
+
+if __name__ == '__main__':
+    m = Manager()
+    with m:
+        print('some execution')
+
+    with m as context:
+        print(f'Execution with context {context}')
+        int('n/a')
+
diff --git a/model.py b/model.py
@@ -0,0 +1,53 @@
+
+class Typed:
+    expected_type = object
+
+    def __init__(self, name):
+        self.name = name
+
+    def __get__(self, instance, cls):
+        return instance.__dict__[self.name]
+
+    def __set__(self, instance, value):
+        if not isinstance(value, self.expected_type):
+            raise TypeError(f'Expected {self.expected_type}')
+        instance.__dict__[self.name] = value
+
+
+class Integer(Typed):
+    expected_type = int
+
+
+class Float(Typed):
+    expected_type = float
+
+
+class Holding:
+    shares = Integer('shares')
+    price = Float('price')
+
+    def __init__(self, name, shares, price):
+        self.name = name
+        self.shares = shares
+        self.price = price
+
+    @property
+    def cost(self):
+        return self.price * self.shares
+
+
+if __name__ == '__main__':
+    h = Holding('IBM', 25, 34.5)
+    print(f'Share {h.shares} : cost : {h.cost}')
+    # h.price = '24'   # TypeError: Expected <class 'float'>
+    # h.shares = 'a lot'  # TypeError: Expected <class 'int'>
+    h.shares = 26
+    print(f'After change: share {h.shares} : cost : {h.cost}')
+
+    # t = Integer('test')
+    # t = 4   # This would override the existing reference
+    # this would work only inside class
+
+    h.append
+
+
