Python Coding Challange - Question with Answer (01230925)

 

Got it 👍 Let’s carefully break this down step by step.

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Code:

a = [1, 2, 3]
for i in a:
 a.remove(i)
print(a)

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🔎 Step-by-Step Execution

1. Initial list:

   a = [1, 2, 3]

2. First iteration:

   i = 1

   • a.remove(1) removes the first occurrence of 1.

   • Now a = [2, 3].

3. Second iteration:

   • The loop moves to the next index (index 1).

   • But since 1 was removed, the list looks like [2, 3].

   • At index 1, the value is now 3.

   • a.remove(3) removes 3.

   • Now a = [2].

4. Loop ends:

   • The iterator thinks it’s done (it already visited index 0 and 1).

   • The last element 2 is skipped because the list was modified.

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✅ Final Output:

[2]

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⚠️ Key Point

• Never modify a list while iterating over it (like remove, append, etc.).

• This causes unexpected behavior because the iterator skips elements.

👉 If you really want to remove items while looping, use a copy of the list:

a = [1, 2, 3]
for i in a[:]:
    a.remove(i) 
print(a) # []

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