python of object-oriented methods and functions, reflection, the method bis

First, the functions and methods

1. The difference between the functions and methods

Function: all dominant mass participation, manual transmission parameters, regardless of the subject

Methods: The existence of hidden mass participation, and related objects

1.1 can be judged by the function name

len()就是函数
str.count()就是方法

def func():
    pass
class A:
    def func(self):

print(func)
obj = A()
print(obj.func()) 

By determining the types module 2.2

from types import functionType
from types import MethodType
print(isinstance(func,FunctionType))
print(isinstance(func,MethodType))

• The class name is a function call func
• The object is to call a method func

2.3 Research for static methods

print(isinstance(A.f, FunctionType)) #指的是函数类型
print(isinstance(A.f, MethodType)) #类方法

Second, reflection

What is the use

There are times when you knew a variable string data type the name you want to call it, but less than a tune, you can use reflection

Reflection method

A string to operate the object by

getattr 获取一个属性或者方法
getattr(obj,'name1',None) #前面是类名,后面是字符串形式的属性或方法

hasattr 判断属性或方法是否存在  
hasattr(obj,'name')

setattr 设置新的属性
setattr(obj,'hobby', '玩')

hasattr 删除属性
hasattr(obj, 'func')

Reflecting object instantiation

Instantiating the object in front of the name, followed by a property of the object instance in the form of a string

class Foo:
    f = '类的静态变量'

    def __init__(self, name, age):
        self.name = name
        self.age = age

    def say_hi(self):
        print(f'hi,{self.name}')

obj = Foo('egon', 73)

# 检测是否含有某属性 name
print(hasattr(obj, 'name'))
print(hasattr(obj, 'say_hi'))

# 获取属性
n = getattr(obj, 'name')  # 等同于 obj.name
print(n)
func = getattr(obj, 'say_hi')
func()

# print(getattr(obj, 'aaaaaaaa', '不存在啊'))  # 报错

# 设置属性
setattr(obj, 'sb', True)  # 等同于 obj.sb = True
setattr(obj, 'show_name', lambda self: self.name + 'sb')
print(obj.__dict__)
print(obj.show_name(obj))

# 删除属性
delattr(obj, 'age')  # 等同于 del obj.age
delattr(obj, 'show_name')
# delattr(obj, 'show_name111')  # 不存在,则报错

print(obj.__dict__)

Reflection of the class

In front of the class name, property or method followed by a string of class

class Foo(object):
    staticField = "old boy"

    def __init__(self):
        self.name = 'wupeiqi'

    def func(self):
        return 'func'

    @staticmethod
    def bar():
        return 'bar'

print(getattr(Foo, 'staticField')) # 前面是类名,后面是类的属性或方法
print(getattr(Foo, 'func'))
print(getattr(Foo, 'bar'))

Reflected current module

import sys

def s1():
    print('s1')

def s2():
    print('s2')

this_module = sys.modules[__name__]  # 比较推荐#sys.modules 获得到的是 当前文件的所有属性及方法，返回是一个字典
# 等同于 this.module = sys.modules["__main__"]

hasattr(this_module, 's1')
getattr(this_module, 's2')()

Reflecting other modules

"""
程序目录：
    module_test.py
    index.py
"""

#  module_test.py   中的代码
def test():
    print('from the test')

# index.py   中的代码
import module_test as obj

# obj.test()

print(hasattr(obj, 'test'))

getattr(obj, 'test')()

class A:

    static_field = '静态属性'

    def __init__(self, name, age):
        self.name = name
        self.age = age

    def func(self):
        print('in A func')


obj = A('MC骚Q', 18)
print(obj.name)
#
print(hasattr(obj,'name'))  # ***
print(getattr(obj,'name1',None))  ***
setattr(obj,'hobby', '玩') *
print(getattr(obj,'hobby'))
print(obj.hobby)
delattr(obj,'name') *
print(hasattr(obj,'name'))
if hasattr(obj, 'static_field'):
    print(getattr(obj,'static_field'))

if hasattr(obj, 'func'):
    # print(getattr(obj,'func'))
    getattr(obj,'func')()

Third, the method of bis

__len__

use

Number of attributes can be acquired class, such as __init__the

format

def __len(self):
    print('触发__len__方法')
    return 10

Trigger method

len(obj)

The reason why an object can use len () function, the root cause is the object class you have from the input __len__method, the method is actually executed ** len when the class is not __len__ this method, using len () will throw an error **

__hash__

use

Hash

Trigger method

print(hash(obj))

__str__method

use

Print output

Trigger method

print(obj)

__repr__method

use

The same __str__as when there is simultaneous with str, str higher priority

Trigger method

print(此对象是%r那就先执行repr的方法)

__call__method

Trigger method

obj() #对象加括号触发就会触发类里面的__call__方法

__eq__method

use

When you are in a class of two objects compare operation, it will trigger __eq__method

__delmethod

What is the use

Object reference for zero time, destructors, automatically deleted

Removed from memory, the garbage collection mechanism ♻️

Call the method

l2 = [1,2,3]
dic = {1:22, 2:33}
del l2
del dic #主动删除

__new__(*****************)

What use

• Constructs an object out (performed automatically __init__when the file is __new__in the dry this thing children)
• Creating build and returns a new space

class A(object):

    def __init__(self):
        print('in __init__')
    def __new__(cls, *args, **kwargs):
        print('in __new__')
        object1 = object.__new__(cls)
        return object1
obj = A()
# 输出结果
in __new__
in __init__

Singleton

Singleton Pattern Singleton pattern is a design pattern, a class intelligent instantiate an object, no matter how many times you instantiate memory are only one object, the purpose is to save space

Interview almost always let you hand a singleton

class A:
    __instance = None

    def __new__(cls, *args, **kwargs):
        if not cls.__instance:
            object1 = object.__new__(cls) 
            cls.__instance = object1
        return cls.__instance
obj = A()
obj1 = A()
obj2 = A()
obj3 = A()
print(obj, obj1, obj2, obj3)

__item__method

use

Operate on an object like a dictionary

__getitem__、__setitem__、__delitem__、

class Foo:
    def __init__(self, name):
        self.name = name

    def __getitem__(self, item):
        print(item)
        print('get时 执行我')

    def __setitem__(self, key, value):
        self.name = value
        print('set时执行我')

    def __delitem__(self, key):
        print(f'del obj{[key]}时,我执行')

obj = Foo('御姐')
# obj.__dict__
# obj['name']
# obj['name'] = '萝莉'
# print(obj.name)
del obj['name']

class Foo:
    def __init__(self, name, key, value):
        self.name = name

        self.dict = {}
        self.dict[key] = value

    def __getitem__(self, key):
        print("1313", self.dict[key])
        # return self.dict[key]

    def __setitem__(self, key, value):
        self.__dict__[key] = value
        print(key, "创建新的键值对")

    def __delitem__(self, key):
        print('del obj[', key, ']时,我执行')
        self.__dict__.pop(key)

    def __delattr__(self, item):
        print('del obj.', item, '时,我执行')
        self.__dict__.pop(item)

f1 = Foo("sb", "A", "1")
f1["A"]  # 会去执行  __getitem__ 方法
f1['age'] = 18  # 会去执行  __setitem__ 方法
f1['age'] = 112  # 修改也会去执行 __setitem__ 方法
f1['age1'] = 250  # 修改也会去执行 __setitem__ 方法
del f1.age1  # 会去执行  __delattr__ 方法
del f1['age']  # 会去执行  __delitem__ 方法
f1['name'] = 'alex'  # 会去执行  __setitem__ 方法
print(f1.__dict__)

Authentication using the class method ***

class Auth:

    function_list = [('login','请登录'),('register','请注册'),('exit_q','退出')]

    def login(self):
        print('欢迎登录')

    def register(self):
        print('欢迎注册')

    def exit_q(self):
        print('退出程序')
        exit()

while 1:
    obj = Auth()
    for num,option in enumerate(obj.function_list,1):
        print(num,option[1])

    try:
        choice_num = input('请输入选择: ').strip()
        if hasattr(obj,obj.function_list[int(choice_num)-1][0]):
            getattr(obj,obj.function_list[int(choice_num)-1][0])()
    except IndexError:
        print('请输入超过范围')
    except ValueError:
        print('请输入数字')