Python Coding Challenge - Question with Answer (ID -171225)

 

Step 1: Create the list

a = [1, 2]

The list has 2 elements:

[1, 2]

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Step 2: a.append(a) (Tricky part )

a.append(a)

• append() adds one single element to the list.

• Here, that element is the list itself (a).

So the list becomes self-referential:

[1, 2, [...]]

([...] means the list contains a reference to itself)

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Step 3: Length of the list

print(len(a))

• Elements are:

  1 
  2
  the list a itself

So:

len(a) = 3
✅ Final Output

3

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Key Concept (Very Important)

• append() adds one object, not multiple elements

• Python stores a reference, not a copy

• Self-referencing lists are allowed in Python

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 Interview Tip

a.append(a) # self-reference
a.extend(a) # infinite loop ❌ (dangerous)

Probability and Statistics using Python