2.6

hexinatgithub · hexinatgithub · commit dc10e8c28ab5 · 2016-10-25T13:12:27.000+08:00
diff --git a/Chapter_2_ Building_Abstractions_with_Data/2.6/2.6.py b/Chapter_2_ Building_Abstractions_with_Data/2.6/2.6.py
@@ -0,0 +1,75 @@
+def make_instance(cls):
+    """Return a new object instance, which is a dispatch dictionary."""
+    def get_value(name):
+        if name in attributes:
+            return attributes[name]
+        else:
+            value = cls['get'](name)
+            return bind_method(value, instance)
+    def set_value(name, value):
+        attributes[name] = value
+    attributes = {}
+    instance = {'get' : get_value, 'set' : set_value}
+
+def bind_method(value, instance):
+    """Return a bound method if value is callable, or value otherwise."""
+    if callable(value):
+        def method(*args):
+            value(instance, *args)
+        return method
+    else:
+        return value
+
+def make_class(attributes, bass_class=None):
+    """Return a new class, which is a dispatch dictionary."""
+    def get_value(name):
+        if name in attributes:
+            return attributes[name]
+        elif bass_class is not None:
+            return bass_class['get'](name)
+    def set_value(name, value):
+        attributes[name] = value
+    def new(*args):
+        return init_instance(cls, *args)
+    cls = {'get' : get_value, 'set' : set_value, 'new' : new}
+    return cls
+
+def init_instance(cls, *args):
+    instance = make_instance(cls)
+    init = cls['get']('__init__')
+    if init:
+        init(instance, *args)
+    return instance
+
+def make_account_class():
+    """Return the Account class, which has deposit and withdraw methods."""
+    interest = 0.02
+    def __init__(self, account_holder):
+        self['set']('holder', account_holder)
+        self['set']('balance', 0)
+    def deposit(self, amount):
+        """Increase the account balance by amount and return the new balance."""
+        new_balance = self['get']('balance') + amount
+        self['set']('balance', new_balance)
+        return self['get']('balance')
+    def withdraw(self, amount):
+        """Decrease the account balance by amount and return the new balance."""
+        balance = self['get']('balance')
+        if amount > balance:
+            return 'Insufficient funds'
+        self['set']('balance', balance - amount)
+        return self['get']('balance')
+    return make_class(locals())
+
+Account = make_account_class()
+
+def make_checking_account_class():
+    """Return the CheckingAccount class, which imposes a $1 withdrawal fee."""
+    interest = 0.01
+    withdraw_fee = 1
+    def withdraw(self, amount):
+        fee = self['get']('withdraw_fee')
+        return Account['get']('withdraw')(self, amount + fee)
+    return make_class(locals(), Account)
+
+CheckingAccount = make_checking_account_class()
