Implement a Private Attribute in a Class

Summary

Practice using Python's name mangling to store a private attribute and expose it safely.

Problem statement

You will implement a simple class SecretNumber that stores a numeric value as a private attribute using Python's double-underscore name mangling (e.g., __value). The class should provide a method reveal() that returns the stored number. The attribute should not be directly accessible via the obvious public attribute name (e.g., obj.value should not exist). This exercise emphasizes how to create a private attribute and access it from within the class.

Task

Create a class that stores a value in a truly private attribute (using double-underscore name mangling) and provide a method that exposes the stored value.

Examples

Input format

A single expression that creates a SecretNumber and calls its reveal() method or inspects attributes (evaluated by the test runner).

Output format

Return the numeric value (or a boolean for attribute-existence checks). The test harness converts the result to string for comparison.

Constraints

Use double-leading-underscore (name mangling) for the private attribute. Do not expose the value as a public attribute named 'value'.

Samples