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Singleton Pattern in Python

Only one instance. Call the constructor twice, get the same object back. People overuse this.

IntermediateObject-Oriented ProgramsExample 23 of 25

singleton-pattern.py

1# Program to implement a simple Singleton pattern
2
3class Singleton:
4    _instance = None
5
6    def __new__(cls, *args, **kwargs):
7        if cls._instance is None:
8            cls._instance = super().__new__(cls)
9        return cls._instance
10
11s1 = Singleton()
12s2 = Singleton()
13
14print(s1 is s2)

Output

True

What's going on

Overriding __new__ ensures that only one instance of Singleton is ever created.

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