Python Coding Challenge - Question with Answer (ID -290126)

 

🔍 What does index() do?

list.index(value, start)
It returns the index of the first occurrence of value,
starting the search from position start.

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Step-by-step execution:

1. arr = [10, 20, 30]
   Index positions:

   0 → 10
   1 → 20
   2 → 30

2. arr.index(20, 1) means:
   👉 Find the value 20, but start searching from index 1.

3. At index 1, the value is 20 → match found.

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✅ Output:

1

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⚠️ Tricky Case (important for quizzes)

arr.index(10, 1)

This will raise:

ValueError: 10 is not in list

Because it starts searching from index 1, and 10 is only at index 0.

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Mental Rule (easy to remember):

index(x, i)

 = "Find x after index i-1"

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