update from Atlas

Author: ramalho

classes/vector_v3.py

@@ -211,8 +211,8 @@ def __getattr__(self, name):
                 return self._components[pos]
         msg = '{.__name__!r} object has no attribute {!r}'  # <5>
         raise AttributeError(msg.format(cls, name))
-
 # END VECTOR_V3_GETATTR
+
 # BEGIN VECTOR_V3_SETATTR
     def __setattr__(self, name, value):
         cls = type(self)

descriptors/bulkfood_v1.py

@@ -0,0 +1,37 @@
+"""
+A line item for a bulk food order has description, weight and price fields.
+A ``subtotal`` method gives the total price for that line item::
+
+    >>> raisins = LineItem('Golden raisins', 10, 6.95)
+    >>> raisins.weight, raisins.description, raisins.price
+    (10, 'Golden raisins', 6.95)
+    >>> raisins.subtotal()
+    69.5
+
+But, without validation, these public attributes can cause trouble::
+
+# BEGIN LINEITEM_PROBLEM_V1
+
+    >>> raisins = LineItem('Golden raisins', 10, 6.95)
+    >>> raisins.subtotal()
+    69.5
+    >>> raisins.weight = -20
+    >>> raisins.subtotal()
+    -139.0
+
+# END LINEITEM_PROBLEM_V1
+
+"""
+
+
+# BEGIN LINEITEM_V1
+class LineItem:
+
+    def __init__(self, description, weight, price):
+        self.description = description
+        self.weight = weight
+        self.price = price
+
+    def subtotal(self):
+        return self.weight * self.price
+# END LINEITEM_V1

descriptors/bulkfood_v2.py

@@ -0,0 +1,63 @@
+"""
+
+A line item for a bulk food order has description, weight and price fields::
+
+    >>> raisins = LineItem('Golden raisins', 10, 6.95)
+    >>> raisins.weight, raisins.description, raisins.price
+    (10, 'Golden raisins', 6.95)
+
+A ``subtotal`` method gives the total price for that line item::
+
+    >>> raisins.subtotal()
+    69.5
+
+The weight of a ``LineItem`` must be greater than 0::
+
+    >>> raisins.weight = -20
+    Traceback (most recent call last):
+        ...
+    ValueError: value must be > 0
+
+No change was made::
+
+    >>> raisins.weight
+    10
+
+The check is also performed on instantiation::
+
+    >>> walnuts = LineItem('walnuts', 0, 10.00)
+    Traceback (most recent call last):
+        ...
+    ValueError: value must be > 0
+
+The proteced attribute can still be accessed if needed for some reason, such as
+white box testing)::
+
+    >>> raisins._LineItem__weight
+    10
+
+"""
+
+
+# BEGIN LINEITEM_V2
+class LineItem:
+
+    def __init__(self, description, weight, price):
+        self.description = description
+        self.weight = weight  # <1>
+        self.price = price
+
+    def subtotal(self):
+        return self.weight * self.price
+
+    @property  # <2>
+    def weight(self):  # <3>
+        return self.__weight  # <4>
+
+    @weight.setter  # <5>
+    def weight(self, value):
+        if value > 0:
+            self.__weight = value  # <6>
+        else:
+            raise ValueError('value must be > 0')  # <7>
+# END LINEITEM_V2

descriptors/bulkfood_v3.py

@@ -0,0 +1,60 @@
+"""
+
+A line item for a bulk food order has description, weight and price fields::
+
+    >>> raisins = LineItem('Golden raisins', 10, 6.95)
+    >>> raisins.weight, raisins.description, raisins.price
+    (10, 'Golden raisins', 6.95)
+
+A ``subtotal`` method gives the total price for that line item::
+
+    >>> raisins.subtotal()
+    69.5
+
+The weight of a ``LineItem`` must be greater than 0::
+
+    >>> raisins.weight = -20
+    Traceback (most recent call last):
+        ...
+    ValueError: value must be > 0
+
+Negative or 0 price is not acceptable either::
+
+    >>> truffle = LineItem('White truffle', 100, 0)
+    Traceback (most recent call last):
+        ...
+    ValueError: value must be > 0
+
+
+No change was made::
+
+    >>> raisins.weight
+    10
+
+"""
+
+# BEGIN LINEITEM_V3
+class Quantity:  # <1>
+
+    def __init__(self, storage_name):
+        self.storage_name = storage_name  # <2>
+
+    def __set__(self, instance, value):  # <3>
+        if value > 0:
+            instance.__dict__[self.storage_name] = value  # <4>
+        else:
+            raise ValueError('value must be > 0')
+
+
+class LineItem:
+    weight = Quantity('weight')  # <5>
+    price = Quantity('price')  # <6>
+
+    def __init__(self, description, weight, price):  # <7>
+        self.description = description
+        self.weight = weight
+        self.price = price
+
+    def subtotal(self):
+        return self.weight * self.price
+# END LINEITEM_V3

descriptors/bulkfood_v3_broken.py

@@ -0,0 +1,59 @@
+"""
+WARNING: Broken implementation for demonstration purposes.
+
+A line item for a bulk food order has description, weight and price fields::
+
+    >>> raisins = LineItem('Golden raisins', 10, 6.95)
+    >>> raisins.weight, raisins.description, raisins.price
+    (10, 'Golden raisins', 6.95)
+
+A ``subtotal`` method gives the total price for that line item::
+
+    >>> raisins.subtotal()
+    69.5
+
+The weight of a ``LineItem`` must be greater than 0::
+
+    >>> raisins.weight = -20
+    Traceback (most recent call last):
+        ...
+    ValueError: value must be > 0
+
+Negative or 0 price is not acceptable either::
+
+    >>> truffle = LineItem('White truffle', 100, 0)
+    Traceback (most recent call last):
+        ...
+    ValueError: value must be > 0
+
+
+No change was made::
+
+    >>> raisins.weight
+    10
+
+"""
+
+class Quantity:
+
+    def __init__(self, storage_name):
+        self.storage_name = storage_name
+
+    def __set__(self, instance, value):
+        if value > 0:
+            instance.__dict__[self.storage_name] = value
+        else:
+            raise ValueError('value must be > 0')
+
+
+class LineItem:
+    weight = Quantity('weight')
+    price = Quantity('weight')  # <-- this is the bug discussed in the book
+
+    def __init__(self, description, weight, price):
+        self.description = description
+        self.weight = weight
+        self.price = price
+
+    def subtotal(self):
+        return self.weight * self.price

descriptors/bulkfood_v4.py

@@ -0,0 +1,74 @@
+"""
+
+A line item for a bulk food order has description, weight and price fields::
+
+    >>> raisins = LineItem('Golden raisins', 10, 6.95)
+    >>> raisins.weight, raisins.description, raisins.price
+    (10, 'Golden raisins', 6.95)
+
+A ``subtotal`` method gives the total price for that line item::
+
+    >>> raisins.subtotal()
+    69.5
+
+The weight of a ``LineItem`` must be greater than 0::
+
+    >>> raisins.weight = -20
+    Traceback (most recent call last):
+        ...
+    ValueError: value must be > 0
+
+No change was made::
+
+    >>> raisins.weight
+    10
+
+The value of the attributes managed by the descriptors are stored in
+alternate attributes, created by the descriptors in each ``LineItem``
+instance::
+
+    >>> raisins = LineItem('Golden raisins', 10, 6.95)
+    >>> dir(raisins)  # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
+    ['_Quantity_0', '_Quantity_1', '__class__', ...
+     'description', 'price', 'subtotal', 'weight']
+    >>> raisins._Quantity_0
+    10
+    >>> raisins._Quantity_1
+    6.95
+
+"""
+
+
+# BEGIN LINEITEM_V4
+class Quantity:
+    __counter = 0  # <1>
+
+    def __init__(self):
+        cls = self.__class__  # <2>
+        prefix = cls.__name__  # <3>
+        index = cls.__counter  # <4>
+        self.storage_name = '_{}_{}'.format(prefix, index)  # <5>
+        cls.__counter += 1  # <6>
+
+    def __get__(self, instance, owner):  # <7>
+        return getattr(instance, self.storage_name)  # <8>
+
+    def __set__(self, instance, value):  # <9>
+        if value > 0:
+            setattr(instance, self.storage_name, value)  # <10>
+        else:
+            raise ValueError('value must be > 0')
+
+
+class LineItem:
+    weight = Quantity()  # <11>
+    price = Quantity()
+
+    def __init__(self, description, weight, price):
+        self.description = description
+        self.weight = weight
+        self.price = price
+
+    def subtotal(self):
+        return self.weight * self.price
+# END LINEITEM_V4

metaprog/spreadsheet.py

@@ -6,7 +6,7 @@
 Demonstration::
 
     >>> from math import sin, pi
-    >>> ss = Spreadsheet(sin=sin, pi=pi, abs=abs)
+    >>> ss = Spreadsheet(sin=sin, pi=pi)
     >>> ss['a1'] = '-5'
     >>> ss['a2'] = 'a1*6'
     >>> ss['a3'] = 'a2*7'
@@ -20,11 +20,6 @@
     >>> ss['c1'] = 'abs(a2)'
     >>> ss['c1']
     30
-    >>> ss['c2'] = 'len(a2)'
-    >>> ss['c2']
-    Traceback (most recent call last):
-      ...
-    NameError: name 'len' is not defined
     >>> ss['d1'] = '3*'
     >>> ss['d1']
     Traceback (most recent call last):
@@ -37,8 +32,7 @@ class Spreadsheet:
 
     def __init__(self, **tools):
         self._cells = {}
-        self._tools = {'__builtins__' : {}}
-        self._tools.update(tools)
+        self._tools = tools
 
     def __setitem__(self, key, formula):
         self._cells[key] = formula

operator/factorial/CorrectFactorial.java

@@ -0,0 +1,49 @@
+import java.math.BigInteger;
+
+class CorrectFactorial {
+    static final BigInteger two = new BigInteger("2");
+
+    public static BigInteger factorial(BigInteger n) {
+        return n.compareTo(two) < 0 ? BigInteger.ONE
+                    : n.multiply(factorial(n.subtract(BigInteger.ONE)));
+    }
+
+    public static void main(String args[]) {
+        BigInteger upperBound = new BigInteger("25"); 
+        for (BigInteger i = BigInteger.ONE;
+                i.compareTo(upperBound) <= 0;
+                i = i.add(BigInteger.ONE)) {
+            System.out.println(i + "! = " + factorial(i));
+        }
+    }
+}
+
+/* output:
+
+1! = 1
+2! = 2
+3! = 6
+4! = 24
+5! = 120
+6! = 720
+7! = 5040
+8! = 40320
+9! = 362880
+10! = 3628800
+11! = 39916800
+12! = 479001600
+13! = 6227020800
+14! = 87178291200
+15! = 1307674368000
+16! = 20922789888000
+17! = 355687428096000
+18! = 6402373705728000
+19! = 121645100408832000
+20! = 2432902008176640000
+21! = 51090942171709440000
+22! = 1124000727777607680000
+23! = 25852016738884976640000
+24! = 620448401733239439360000
+25! = 15511210043330985984000000
+
+*/