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.
Exhibit
>>> x = 10
>>> y = "20"
>>> print(x + y)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
Refer to the exhibit. A beginner Python programmer executes the code and gets an error. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
>>> x = 10
>>> y = "20"
>>> print(x + y)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
A
The variables x and y are of incompatible types for the + operator
Correct: int and str cannot be added with +
B
The + operator cannot be used with print()
Why wrong: The + operator is valid inside print(); the issue is type mismatch
C
The variable y should be converted to an integer using int()
Why wrong: This is a fix, not the cause of the error
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The variables x and y are of incompatible types for the + operator
Option A is correct because the error occurs when the + operator is used between incompatible types, such as a string (x) and an integer (y). In Python, the + operator performs concatenation for strings and addition for numbers, but mixing types without explicit conversion raises a TypeError. The code likely defines x as a string (e.g., '10') and y as an integer (e.g., 5), causing the error.
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.
✓
The variables x and y are of incompatible types for the + operator
Why this is correct
Correct: int and str cannot be added with +
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The + operator cannot be used with print()
Why it's wrong here
The + operator is valid inside print(); the issue is type mismatch
✗
The variable y should be converted to an integer using int()
Why it's wrong here
This is a fix, not the cause of the error
✗
The print function is misspelled
Why it's wrong here
print is spelled correctly
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the misconception that the + operator can automatically convert types, leading candidates to overlook the need for explicit type conversion or to incorrectly blame the print function.
Detailed technical explanation
How to think about this question
Under the hood, Python's + operator invokes the __add__ method of the left operand, and if the types are incompatible, it raises a TypeError. A subtle behavior is that Python does not implicitly convert strings to integers or vice versa for +, unlike some other languages (e.g., JavaScript). In real-world scenarios, this often occurs when reading user input (which is always a string) and attempting to add it to a numeric value without explicit conversion.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: The variables x and y are of incompatible types for the + operator — Option A is correct because the error occurs when the + operator is used between incompatible types, such as a string (x) and an integer (y). In Python, the + operator performs concatenation for strings and addition for numbers, but mixing types without explicit conversion raises a TypeError. The code likely defines x as a string (e.g., '10') and y as an integer (e.g., 5), causing the error.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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