Python Coding Challange - Question with Answer (01151025)

 

🔍 Step-by-step explanation

1. a = np.array([1, 2, 3, 4])
   Creates a NumPy array:

   a = [1, 2, 3, 4]

2. [True, False, True, False]
   → This is a boolean mask.
   Each boolean value corresponds to whether to select (True) or ignore (False) the element at that index.

3. Boolean indexing:
   NumPy uses the boolean mask to filter elements:

   • Index 0 → True → select 1

   • Index 1 → False → skip 2

   • Index 2 → True → select 3

   • Index 3 → False → skip 4

4. Result:

   [1, 3]

✅ Output:

[1 3]

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🧠 Concept:

This is called Boolean Indexing in NumPy — a powerful feature that lets you filter arrays based on conditions.

For example:

a = np.array([10, 20, 30, 40])
print(a[a > 20])

Output:

[30 40]

👉 NumPy automatically creates a boolean mask [False, False, True, True] and returns elements where the condition is True.

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