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Given the following Singleton implementation with eager initialization, what will be the output of the print statement when run?

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OOP & Design Patterns - Singleton Pattern - Thread Safety, Double-Checked Locking & Lazy Init
Given the following Singleton implementation with eager initialization, what will be the output of the print statement when run?
ATrue
BRaises Exception
CFalse
DNone
Step-by-Step Solution
Solution:

  1. Step 1: Trace instance creation for s1

    _instance is eagerly created and returned for s1.

  2. Step 2: Trace instance creation for s2

    _instance is returned again for s2, same object.

  3. Final Answer:

    Option A -> Option A

  4. Quick Check:

    Both s1 and s2 reference the same eagerly created instance [OK]
Quick Trick: Eager init returns same pre-created instance always [OK]
Common Mistakes:
MISTAKES
  • Assuming new instance created on each call
Trap Explanation:
PITFALL
  • Candidates may think __new__ creates new object each time ignoring _instance reuse.
Interviewer Note:
CONTEXT
  • Tests tracing eager singleton behavior on edge case input
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