加入类Point, Rectangle, Time

1 files changed, 152 insertions, 1 deletions

diff --git a/LectureNotesOnPython.rst b/LectureNotesOnPython.rst
index 36a1eb3..fac7727 100644
--- a/LectureNotesOnPython.rst
+++ b/LectureNotesOnPython.rst
@@ -1520,9 +1520,160 @@ Memo
 类 class 与 对象 object
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+程序员用类（class）来定义一类数据。
+
+.. code:: python
+
+         class Point:
+             """Represents a point in 2-D space."""
+         
+         
+         blank = Point()
+         
+         blank.x = 1  # an attribute
+         blank.y = 2  # an attribute
+         x = blank.x
+         
+         
+         def print_point(p):
+             print('(%g, %g)' % (p.x, p.y))
+         
+         def reset_point(p): # object is Mutable
+             p.x = 0
+             p.y = 0
+             
+         print_point(blank)
+         reset_point(blank)
+         print_point(blank)
+                  
+
+blank 是（指向） Point类型的对象的一个变量。  注意到Point后面跟随了括
+号， 是对类的实例化 （instantiation）。 我们说 blank 是Point类的一个实
+例 （instance）， 也可以说是Point类的一个对象。  
+
+对象是Mutable类型数据。 如 reset_point 所示。
+
+
+一个对象可以是另外一个对象的属性
+````````````````````````````````````````````````````
+
+.. code:: python
+
+         class Point:
+             def __init__(self, x, y):
+                 self.x = x
+                 self.y = y
+                 
+             def __str__(self):
+                 return '(%g, %g)' % (self.x, self.y)
+         
+         
+         class Rectangle:
+             def __init__(self, lower_left_corner, width, height):
+                 self.lower_left_corner = lower_left_corner # lower_left_corner is a Point object
+                 self.width = width
+                 self.height = height
+                 
+             def get_center(self):
+                 return Point(self.lower_left_corner.x + self.width/2, self.lower_left_corner.y + self.height/2)
+             
+                 
+         class Circle:
+             def __init__(self, center, radius):
+                 self.center = center # center is a Point object
+                 self.r = radius
+         
+         
+         r = Rectangle(Point(0,0), 10, 4)
+         print(r.get_center())
+         
+
+
+copy 与 deepcopy
+````````````````````````````````````````````````````
+
+copy 拷贝类中的属性， 但不会重新制作一个对象中的对象 （embedded object），而是拷贝其引用而已。 而deepcopy会。
+
+
+.. code:: python
+
+
+         import copy
+         
+         class Point:
+             def __init__(self, x, y):
+                 self.x = x
+                 self.y = y
+                 
+             def __str__(self):
+                 return '(%g, %g)' % (self.x, self.y)
+             
+             def __eq__(self, other):
+                 return self.x == other.x and self.y == other.y
+                 
+         
+         class Rectangle:
+             def __init__(self, lower_left_corner, width, height):
+                 self.lower_left_corner = lower_left_corner # lower_left_corner is a Point object
+                 self.width = width
+                 self.height = height
+                 
+                 
+         p1 = Point(1, 2)
+         p2 = copy.copy(p1)
+         
+         print(p1 is p2)
+         print(p1 == p2) # what if we don't have the __eq__ method
+         
+         r1 = Rectangle(Point(0,0), 10, 4)
+         r2 = copy.copy(r1)
+         print(r1 is r2) # False
+         print(r1.lower_left_corner is r2.lower_left_corner) # True
+         print(r1.width is r2.width) # also True
+         
+         r1.width = 20
+         print(r1.width is r2.width)
+         print(r2.width)  # remain to be 10
+         
+         r1 = Rectangle(Point(1,1), 8, 4)
+         r3 = copy.deepcopy(r1)
+         print(r1 is r3) # False
+         print(r1.lower_left_corner is r2.lower_left_corner) # False
+
+
+         
+纯函数与修改函数
+````````````````````````````````````````````````````
+
+.. code:: python
+
+
+         class Time:
+             def __init__(self, h, m, s):
+                 self.hour = h
+                 self.minute = m
+                 self.second = s
+                 
+         
+         def increment_time_pure(t, h, m, s):
+             ''' Pure function '''
+             t2 = Time(0,0,0)
+             return t2
+         
+         def increment_time_modifier(t, h, m, s):
+             ''' Modifier function '''
+             t2 = Time(0,0,0)
+             return t2
+         
+         t = Time(6, 58, 55)
+         ti = increment_time_pure(t, 2, 30, 50)
+         
+         
+
+
 
 web 应用程序
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+````````````
 
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