Python Learning Notes (vii)-object-oriented advanced programming

I. Adding properties and methods to a class dynamically:

1. Dynamically add properties and methods to an instance:

The method that is bound to one instance has no effect on the other.

Class Student (object):    passs = Student () s.name = ' Michael ' # dynamically binds an attribute to an instance print S.namedef set_age (self, Age): # defines a function as Instance method    Self.age = age from    types import methodtypes.set_age = Methodtype (Set_age, S, Student) # Binds a method to an instance s.set_age ( 25) # Call instance method print S.age # test Result

2. Dynamically add properties and methods to a class:

Class Student (object):    passs = Student () from types import methodtypedef Set_score (self, score):    Self.score = Score    Student.set_score = Methodtype (Set_score, None, Student) s.set_score (+) Print S.score

Two. Using __slots__

Use __slots__ to limit the attributes that class can add:

Class Student (object):    __slots__ = (' name ', ' age ') # define the property name to allow binding with tuple S = Student () # Create a new instance S.name = ' Michael ' # binding attribute ' Name ' S.age = 25 # Binding attribute ' age '

Note: The properties defined by __slots__ only work for the current class and do not work on inherited subclasses.

Three. Using @property

@property is responsible for turning a method into a property invocation:

Class Student (object):    @property    def score (self):        return Self._score    @score. Setter    def score ( Self, value):        if not isinstance (value, int):            raise ValueError (' score must is an integer! ')        If value < 0 or value >:            raise ValueError (' score must between 0 ~ 100! ')        Self._score = value        s = Student () S.score = OK, actual conversion to S.set_score () print S.score # OK, actual conversion to S.get_score ()

Four. Multiple inheritance:

Python allows the use of multiple inheritance, for example: Dog inherits Animal and runnable

Class Animal (object):    passclass Runnable (object):    def run (self):        print (' Running ... ')        class Dog ( Animal, Runnable):    Pass

Five. Custom classes:

1. __str__

Equivalent to ToString in Java

Class Student (object):    def __init__ (self, name):        self.name = name        def __str__ (self):        return ' Student Object (name:%s) '% self.nameprint Student (' Michael ') # Student object (Name:michael)

2.__iter__

If a class wants to become a list or a tuple can be cycled (for. In), you must implement the __iter__ method, which returns an iterative object and constantly calls the next () method of the iteration object to get the next value of the loop:

Class Fib (object):    def __init__ (self):        self.a, self.b = 0, 1 # Initializes two counters A, a    def __iter__ (self):        return The self # instance itself is an iterative object, so return your    def next:        self.a, self.b = self.b, SELF.A + self.b # Calculates the next value        if SELF.A > 10000 0: # Exit the condition of the loop            raise Stopiteration ();        Return SELF.A # Returns the next value for    N in Fib ():    print N

3.__getitem__

4.__getattr__

5.__call__

Six. Use meta-classes:

Python Learning Notes (vii)-object-oriented advanced programming