Quick Answer
The correct answer is Option B, which uses `float(input())` to read float input and compute square with the `**` operator. This works because `input()` always returns a string, so it must be wrapped in `float()` to convert the user’s typed number into a floating-point value that supports decimal arithmetic. The exponentiation operator `**` then raises that number to the power of 2, giving the square. On the Certified Entry-Level Python Programmer PCEP exam, this question tests your understanding of type conversion and arithmetic operators—two foundational skills for handling numeric input. A common trap is forgetting to convert the input string, which would cause a TypeError when trying to square a string, or using `^` instead of `**`, since `^` is a bitwise XOR, not exponentiation. To remember: always think “float first, then double star for square”—the `**` operator is your exponent shortcut, and `float()` ensures decimals are preserved.
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.
A developer wants to read a floating-point number from user input and compute its square. Which code snippet correctly accomplishes this?
num = input(); result = num * num
Why wrong: Incorrect: string multiplication repeats string.
num = float(input()); result = num ** 2
Correct: converts input to float.
result = input() ** 2
Why wrong: Incorrect: cannot exponentiate string.
num = int(input()); result = num ** 2
Why wrong: Incorrect: int() fails on decimals.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
num = float(input()); result = num ** 2
Option B is correct because it uses `float(input())` to convert the user's input (which is always a string) into a floating-point number, and then computes the square using the exponentiation operator `**`. This ensures that decimal values are handled correctly, which is required for computing the square of a floating-point number.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
num = input(); result = num * num
Why it's wrong here
Incorrect: string multiplication repeats string.
num = float(input()); result = num ** 2
Why this is correct
Correct: converts input to float.
Related concept
Read the scenario before looking for a memorised answer.
result = input() ** 2
Why it's wrong here
Incorrect: cannot exponentiate string.
num = int(input()); result = num ** 2
Why it's wrong here
Incorrect: int() fails on decimals.
Common exam traps
Python Institute often tests the misconception that `input()` returns a numeric type, leading candidates to forget explicit conversion and choose options that attempt arithmetic on strings.
Detailed technical explanation
In Python, `input()` always returns a string, so explicit type conversion with `float()` or `int()` is necessary for numeric operations. The `**` operator performs exponentiation and works with both integers and floats; for example, `float('3.5') ** 2` yields `12.25`. A subtle behavior is that `float()` can also parse strings like 'inf' or 'nan', which could lead to unexpected results if input validation is not performed.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
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..
The correct answer is: num = float(input()); result = num ** 2 — Option B is correct because it uses `float(input())` to convert the user's input (which is always a string) into a floating-point number, and then computes the square using the exponentiation operator `**`. This ensures that decimal values are handled correctly, which is required for computing the square of a floating-point number.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A developer writes a script to read user input using input() and then prints it. However, the program crashes when the user enters a number. What is the most likely cause?
easyWhy A: The `input()` function in Python 3 always returns a string, regardless of what the user types. If the user enters a number, the program may crash if the code later performs an operation (like arithmetic or comparison) on that string without first converting it to an integer or float using `int()` or `float()`. This mismatch between the string type and the expected numeric type causes a `TypeError`.
Last reviewed: Jun 30, 2026
This PCEP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCEP exam.
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