[Solved] What is the problem with this Flask Singleton pattern implementation? ```python class Config:... What is the problem with this Flask Singleton pattern implementation? | Flask

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What is the problem with this Flask Singleton pattern implementation? ```python class Config: _instance = None def __new__(cls): if cls._instance is None: cls._instance = super().__new__(cls) return cls._instance config1 = Config() config2 = Config() print(config1 is config2) ```

AThe _instance variable should be defined inside __init__, not at class level

BThe __new__ method should return a new object every time, not the same instance

CThe Singleton pattern is correctly implemented; both instances are the same

DThe print statement will raise an error because 'is' cannot compare objects

Step-by-Step Solution

Solution:

Step 1: Review Singleton pattern
Singleton ensures only one instance of a class exists.
Step 2: Analyze code
The __new__ method checks if _instance is None and creates it once, returning the same instance thereafter.
Step 3: Check print output
config1 and config2 refer to the same object, so 'config1 is config2' prints True.
Final Answer:
The Singleton pattern is correctly implemented; both instances are the same -> Option C
Quick Check:
Singleton returns same instance every time [OK]

Quick Trick: Singleton returns same instance on multiple calls [OK]

Common Mistakes:

MISTAKES

Thinking __new__ should always create new objects
Placing _instance inside __init__ instead of class level
Believing 'is' cannot compare objects

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What is the problem with this Flask Singleton pattern implementation?

Step 1: Review Singleton pattern

Step 2: Analyze code

Step 3: Check print output

Final Answer:

Quick Check:

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