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Python Design Patterns - Singleton
Neha Kumawat
2 years ago
This pattern restricts the instantiation of a class to one object. It is a type of creational pattern and involves only one class to create methods and specified objects.
It provides a global point of access to the instance created.
How to implement a singleton class?
The following program demonstrates the implementation of singleton class where it prints the instances created multiple times.
class Singleton:
__instance = None
@staticmethod
def getInstance():
""" Static access method. """
if Singleton.__instance == None:
Singleton()
return Singleton.__instance
def __init__(self):
""" Virtually private constructor. """
if Singleton.__instance != None:
raise Exception("This class is a singleton!")
else:
Singleton.__instance = self
s = Singleton()
print s
s = Singleton.getInstance()
print s
s = Singleton.getInstance()
print s
Output
The above program generates the following output −
The number of instances created are same and there is no difference in the objects listed in output.