8、 Python learning notes - object oriented - singleton mode

# The singleton pattern ： Always use the same instance （ object ）
""" Application scenarios
1、 When creating resources to be reused in the course , Use the same instance , Avoid creating too many objects that waste time and resources
"""
# Example 1、 Demo singleton mode
class Foo:
__bar = None
@classmethod
def bar(cls):
if cls.__bar:
return cls.__bar
else:
cls.__bar = Foo() # In fact, the instantiation here
return cls.bar()
"""
1、 Do not use in singleton mode obj = class() Create objects this way ( In fact, the object is cls.__bar = Foo() Created here )
2、 The following code is just calling an object method , No matter how many calls are made, the same object （ example ） Methods , So the result is the same
"""
foo1 = Foo.bar()
print(foo1)
foo2 = Foo.bar()
print(foo2)
foo3 = Foo.bar()
print(foo3)