Python class attribute delay calculation, python attribute Delay

Python class attribute delay calculation, python attribute Delay

The so-called latency Calculation of class attributes defines the class attributes as a property, which is calculated only when accessed. Once accessed, the results will be cached, you do not need to calculate it every time.

Advantages

The main purpose of constructing a delayed computing attribute is to improve performance.

Implementation

class LazyProperty(object):  def __init__(self, func):    self.func = func  def __get__(self, instance, owner):    if instance is None:      return self    else:      value = self.func(instance)      setattr(instance, self.func.__name__, value)      return valueimport mathclass Circle(object):  def __init__(self, radius):    self.radius = radius  @LazyProperty  def area(self):    print 'Computing area'    return math.pi * self.radius ** 2  @LazyProperty  def perimeter(self):    print 'Computing perimeter'    return 2 * math.pi * self.radius

Description

Defines a LazyProperty class for delayed computing. Circle is used for testing. The Circle class has three attributes: radius, area, and perimeter ). LazyProperty is decorated with the property of area and perimeter. Let's try the magic of LazyProperty:

>>> c = Circle(2)>>> print c.areaComputing area12.5663706144>>> print c.area12.5663706144

"Computing area" is printed every time calculated in area (). After Calling c. area twice in a row, "Computing area" is printed only once. This benefits from LazyProperty. After a call, no matter how many subsequent calls are called, the calculation will not be repeated.

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