Python – What Is Singleton Class ?
Table Of Content:
- What Is Singleton Class ?
- Example Of Singleton Class.
- Where Do We Use Singleton Class?
- Why Do We Want To Use Singleton Class?
- Advantages Of Singleton Class.
- When Not To Use Singleton Class?
- One Liner Summary.
(1) What Is Singleton Class ?
(2) Example Of Singleton Class .
(3) Where Do We Use Singleton Class ?
(4) Why Do We Want To Use A Singleton?
(5) Advantages Of Singleton Class.
(6) When Not To Use Singleton Class ?
(7) One-liner summary
(8) Let’s Compare BEFORE vs AFTER Singleton For Each
(9) Python Example Of Singleton Classes .
Singleton Pattern: Common Decorator:
import os
def singleton(cls):
instances = {}
def _singleton(*args, **kwargs):
key = str(cls) + str(os.getpid())
if key not in instances:
instances[key] = cls(*args, **kwargs)
return instances[key]
return _singleton
Example-1: Logger Singleton
@singleton
class Logger:
def __init__(self):
self.log_file = open('app.log', 'a')
print("Logger instance created!")
def log(self, message):
self.log_file.write(message + '\n')
self.log_file.flush()
Example-2: Logger Singleton
@singleton
class Config:
def __init__(self):
print("Loading config...")
self.api_key = "SECRET_API_KEY"
self.env = "production"
Example-3: Database Connection Pool Singleton (Mock)
@singleton
class DBConnectionPool:
def __init__(self):
print("DB Connection Pool created!")
self.connections = ["conn1", "conn2", "conn3"]
def get_connection(self):
return self.connections.pop() if self.connections else None
