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built-in properties
Use the built-in function dirto view all the properties and methods supported by an object. There are many built-in properties in Python.
__slots__
Python supports dynamic attributes, you can directly add attributes to an object through dot syntax, and the code is more flexible. But in some cases, we may need to control the properties, at this time, we can use __slots__the implementation.
class Person(object):
__slots__ = ('name', 'age')
def __init__(self, name, age):
self.name = name
self.age = age
p = Person('张三', 18)
p.name = '李四'
# 对象p只能设置name和age属性，不能再动态添加属性
# p.height = 180 # 报错
__doc__
Indicates the descriptive information of the class.
class Foo:
""" 描述类信息，这是用于看片的神奇 """
def func(self):
pass
print(Foo.__doc__)
# 输出：类的描述信息
__module__and __class__
__module__Indicates which module the object of the current operation is in; __class__what is the class of the object of the current operation.
test.py
class Person(object):
def __init__(self):
self.name = 'laowang'
main.py
from test import Person
obj = Person()
print(obj.__module__) # 输出 test 即：输出模块
print(obj.__class__) # 输出 test.Person 即：输出类
__dict__
In the form of a dictionary, display all the properties and methods of the object.
class Province(object):
country = 'China'
def __init__(self, name, count):
self.name = name
self.count = count
def func(self, *args, **kwargs):
print('func')
# 获取类的属性，即：类属性、方法、
print(Province.__dict__)
# 输出：{'__dict__': <attribute '__dict__' of 'Province' objects>, '__module__': '__main__', 'country': 'China', '__doc__': None, '__weakref__': <attribute '__weakref__' of 'Province' objects>, 'func': <function Province.func at 0x101897950>, '__init__': <function Province.__init__ at 0x1018978c8>}
obj1 = Province('山东', 10000)
print(obj1.__dict__)
# 获取 对象obj1 的属性
# 输出：{'count': 10000, 'name': '山东'}
obj2 = Province('山西', 20000)
print(obj2.__dict__)
# 获取 对象obj1 的属性
# 输出：{'count': 20000, 'name': '山西'}
__getitem__, __setitem__and __delitem__methods
These three methods operate on the object as a dictionary.
class Foo(object):
def __getitem__(self, key):
print('__getitem__', key)
def __setitem__(self, key, value):
print('__setitem__', key, value)
def __delitem__(self, key):
print('__delitem__', key)
obj = Foo()
result = obj['k1'] # 自动触发执行 __getitem__
obj['k2'] = 'laowang' # 自动触发执行 __setitem__
del obj['k1'] # 自动触发执行 __delitem__
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