There are two forms of class members
Publicly owned members, accessible from anywhere
Private members, which can only be method inside the class, are named with the first two characters being underscores.
class Foo:
def __init__(self, name, age):
= name
self.__age = age
def show(self): # Indirect method private fields
return self.__age
obj = Foo('klvchen', 25)
print()
res = ()
print(res)
Run results:
klvchen
25
Public static fields: accessible by class; accessible within class; accessible in derived classes
Private static fields: accessible only inside the class;
class Foo:
__v = '666' # Private static fields
def __init__(self):
pass
def show(self):
return Foo.__v
obj = Foo()
res = ()
print(res)
Results.
666
class Foo:
__v = '666'
def __init__(self):
pass
def show(self):
return Foo.__v
@staticmethod
def stat():
return Foo.__v
res = ()
print(res)
Results.
666
Unable to inherit private fields from parent class
class F:
def __init__(self):
= 123
self.__gene = 456 # Private fields
class S(F):
def __init__(self, name):
= name
self.__age = 18
super(S, self).__init__()
def show(self):
print()
print(self.__age)
print()
print(self.__gene)
s = S('klvchen')
()
Results.
klvchen
18
123
AttributeError: 'S' object has no attribute '_S__gene'
Special members of a class
int(object), will automatically execute the __int__ method in the object, and will return the assignment to the int object, the same way str(object), will automatically execute the __str__ method, and return the assignment to the str object.
class Foo:
def __init__(self):
pass
def __int__(self):
return 666
def __str__(self):
return 'hello world'
obj = Foo()
print(obj, type(obj))
res = int(obj)
print(res)
res1 = str(obj)
print(res1)
Results.
<__main__.Foo object at 0x0000022BBE9DA978> <class '__main__.Foo'>
666
hello world
print(object), str(object), all automatically execute the __str__ method in the object and return the
class Foo:
def __init__(self, n, a):
= n
= a
def __str__(self):
return '%s-%d' %(, )
obj = Foo('klvchen', 28)
print(obj)
Run results:
klvchen-28
When two objects are added together, the __add__ method of the first object is automatically executed and the second object is passed in as a parameter
class Foo:
def __init__(self, name, age):
= name
= age
def __add__(self, other):
return +
obj1 = Foo('klv1', 23)
obj2 = Foo('klv2', 24)
res = obj1 + obj2
print(res, type(res))
Results.
47 <class 'int'>
class Foo:
def __init__(self, name, age):
= name
= age
def __add__(self, other):
return Foo(, )
def __del__(self):
print('Deconstruction method')
obj1 = Foo('klv1', 23)
obj2 = Foo('klv2', 24)
res = obj1 + obj2
print(res, type(res))
Results.
<__main__.Foo object at 0x0000016DFCE125C0> <class '__main__.Foo'>
destructuring method
destructuring method
destructuring method
li[object] automatically executes the __getitem__ method of the class of the li object, passing 8 as an argument to item
class Foo:
def __init__(self, name, age):
= name
= age
def __getitem__(self, item):
return item
li = Foo('klvchen', 28)
r = li[8]
print(r)
Results.
8
The __setitem__,__delitem__ methods in the class
class Foo:
def __init__(self, name, age):
= name
= age
def __getitem__(self, item):
return item
def __setitem__(self, key, value):
print(key, value)
def __delitem__(self, key):
print(key)
li = Foo('klvchen', 28)
r = li[8]
print(r)
li[100] = 'hello'
del li[999]
Results.
8
100 hello
999
Execute the __iter__() method in the class and get its return value, return the object in the previous step of the loop for the iterator, the reason why lists, dictionaries, and tuples can be subject to for loops is because of the internal definition of the type iter
class Foo:
def __init__(self, name, age):
= name
= age
def __iter__(self):
return iter([11, 22, 33])
li = Foo('klvchen', 26)
for i in li:
print(i)
Results.
11
22
33
The inner workings of a for loop
obj = iter([11, 22, 33]) while True: val = () print val
summarize
The above is a small introduction to the Python class of special members of the analysis, I hope to help you, if you have any questions please leave me a message, I will promptly reply to you. Here also thank you very much for your support of my website!