PCEP Practice Question: Data Types, Variables, Basic I/O and Operators
A developer writes code to compute the average of two numbers entered by the user: x = input('Enter first number: '); y = input('Enter second number: '); avg = (x + y) / 2. The program produces an error. What is the best practice to fix the code?
⚠ Common exam trap
Python Institute often tests the misconception that `input()` returns a numeric type, leading candidates to pick Option B (using `int`) or Option C (casting inside the expression), but the trap is that string concatenation happens before any conversion, so the error occurs at the `+` operator, not at the division.
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
✓
Convert x and y to float before the operation: x = float(input(...)); y = float(input(...))
The `input()` function in Python always returns a string. When you use the `+` operator on two strings, it concatenates them (e.g., '5' + '3' = '53'), not adds them numerically. Dividing a concatenated string by 2 raises a TypeError. The best practice is to convert both inputs to `float` immediately after receiving them, ensuring the subsequent arithmetic works correctly.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Convert the result to int after the operation: avg = int((x + y) / 2)
Why it's wrong here
This does not solve the string concatenation issue; x + y would concatenate strings.
- ✗
Use int() on the input() values: x = int(input(...)); y = int(input(...))
Why it's wrong here
This works only if the input is a whole number, but the problem does not specify integers.
- ✗
Use type casting in the division: avg = (float(x) + float(y)) / 2
Why it's wrong here
This would work but is less efficient than converting once; however, the order is correct, so this could also work but is not best practice because it repeats conversion.
- ✓
Convert x and y to float before the operation: x = float(input(...)); y = float(input(...))
Why this is correct
This ensures the addition and division work on numeric values.
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