PCEP Practice Question: Data Types, Variables, Basic I/O and Operators
A programmer needs to swap the values of two variables a and b without using a temporary variable. Which approach works in Python?
⚠ Common exam trap
Python Institute often tests the misconception that simple sequential assignment (a = b; b = a) works for swapping, leading candidates to overlook Python's tuple unpacking mechanism.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
a, b = b, a
Python supports tuple unpacking, which allows the values of a and b to be swapped in a single atomic operation: a, b = b, a. This works by creating a tuple (b, a) on the right-hand side, then unpacking it into the variables on the left, effectively swapping the values without a temporary variable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
a = b; b = a
Why it's wrong here
Incorrect: both end up with same value.
- ✓
a, b = b, a
Why this is correct
Correct: Python's tuple unpacking swaps values.
- ✗
a = a ^ b; b = a ^ b; a = a ^ b
Why it's wrong here
Incorrect: works but not recommended; also fails for non-int.
- ✗
a = b + a; b = a - b; a = a - b
Why it's wrong here
Incorrect: this only works for numbers and is error-prone.
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