PCEP Practice Question: Data Types, Variables, Basic I/O and Operators
This PCEP practice question tests your understanding of data types, variables, basic i/o and operators. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are maintaining a legacy Python 2.7 script that calculates shipping costs. The script reads weight from user input, then calculates cost as weight * 1.5. Recently, the company upgraded to Python 3.9, and now the script raises a TypeError: can't multiply sequence by non-int of type 'float'. The input line is: weight = input('Enter weight: '). You need to fix the script minimally. Which action should you take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the input line to weight = float(input('Enter weight: '))
In Python 3.9, `input()` returns a string, not a number. Multiplying a string by a float raises a TypeError. Option D converts the input to a float immediately, which is the minimal fix because it handles both integer and decimal weights correctly without changing the multiplication logic.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use Python 2 style input by importing from __future__
Why it's wrong here
Python 2's input() evaluates expression, which is a security risk; not recommended.
✗
Change the multiplication to cost = float(weight) * 1.5
Why it's wrong here
Although it works, it's less efficient and doesn't fix the root cause; also weight remains string for later use.
✗
Change the input line to weight = int(input('Enter weight: '))
Why it's wrong here
int() would fail if weight contains decimal point; also loses precision.
✓
Change the input line to weight = float(input('Enter weight: '))
Why this is correct
Converts string to float, allowing multiplication.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the difference between Python 2 and Python 3 `input()` behavior, and the trap here is that candidates might choose `int()` (Option C) thinking weights are always whole numbers, or choose `from __future__` (Option A) without realizing it does not fix the type mismatch in Python 3.
Detailed technical explanation
How to think about this question
In Python 2, `input()` evaluated the input as a Python expression, so typing `2.5` would return a float. Python 3 removed this behavior for security and consistency, making `input()` always return a string. The TypeError occurs because Python cannot implicitly convert a string to a number when multiplying by a float; explicit conversion with `float()` is required. This change is a common migration issue when moving from Python 2 to Python 3.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the PCEP exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Data Types, Variables, Basic I/O and Operators — This question tests Data Types, Variables, Basic I/O and Operators — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change the input line to weight = float(input('Enter weight: ')) — In Python 3.9, `input()` returns a string, not a number. Multiplying a string by a float raises a TypeError. Option D converts the input to a float immediately, which is the minimal fix because it handles both integer and decimal weights correctly without changing the multiplication logic.
What should I do if I get this PCEP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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