Quick Answer
The output is correct as is because the f-string format specifier `.3g` instructs Python to display the number with exactly 3 significant digits using the general format, which for `0.123456789` correctly yields `'0.123'`. The `g` type automatically chooses between fixed-point and scientific notation based on the magnitude of the number, and for small exponents like this, it stays in fixed-point form, preserving the leading zero and trimming after the third significant digit. On the Certified Associate Python Programmer PCAP exam, this tests your understanding of f-string formatting significant digits and how the `g` specifier differs from `f` or `e` — a common trap is confusing significant digits with decimal places, thinking `.3g` would round to three decimal places instead. Remember: `g` counts all digits from the first non-zero, while `f` counts digits after the decimal point. A quick memory tip: “g for general, f for fixed, e for exponent” — and with `g`, the leading zero before the decimal does not count as a significant digit.
This PCAP practice question tests your understanding of strings. 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 team is using f-strings to format a report. They have a variable `value = 0.123456789` and want to display it with exactly 3 significant digits. They write `f"{value:.3g}"`. The output is '0.123'. They expected '0.123'. Is the output correct? If not, what change would produce '0.123'?
Use `f"{value:.3s}"`
Why wrong: `.3s` is for string truncation, not applicable to floats.
Use `f"{value:.3f}"`
Why wrong: `.3f` would give '0.123' as fixed-point with 3 decimal places, same output but different format.
Use `f"{value:.3e}"`
Why wrong: `.3e` produces scientific notation '1.235e-01', not '0.123'.
The output is correct as is.
`.3g` specifies 3 significant digits, which yields '0.123'.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The output is correct as is.
Option D is correct because the format specifier `.3g` in an f-string instructs Python to format the number with 3 significant digits using general format. For `0.123456789`, the first three significant digits are '123', and the general format automatically switches to fixed-point notation when the exponent is small, producing '0.123' exactly as expected.
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.
Use `f"{value:.3s}"`
Why it's wrong here
`.3s` is for string truncation, not applicable to floats.
Use `f"{value:.3f}"`
Why it's wrong here
`.3f` would give '0.123' as fixed-point with 3 decimal places, same output but different format.
Use `f"{value:.3e}"`
Why it's wrong here
`.3e` produces scientific notation '1.235e-01', not '0.123'.
The output is correct as is.
Why this is correct
`.3g` specifies 3 significant digits, which yields '0.123'.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse 'significant digits' (controlled by `g`) with 'decimal places' (controlled by `f`), leading them to incorrectly choose `.3f` when `.3g` is the correct specifier for significant digits.
Trap categories for this question
Command / output trap
`.3f` would give '0.123' as fixed-point with 3 decimal places, same output but different format.
Detailed technical explanation
The `g` format type uses the smaller of fixed-point and scientific notation, and it strips trailing zeros after the decimal point. The number of significant digits is controlled by the precision specifier; for `0.123456789`, the general format yields '0.123' because the exponent is -1, keeping the fixed-point representation. A subtle behavior: if the value were 0.000123456, `.3g` would output '0.000123' (three significant digits), while `.3f` would output '0.000' (zero significant digits), highlighting the difference.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Strings — This question tests Strings — Read the scenario before looking for a memorised answer..
The correct answer is: The output is correct as is. — Option D is correct because the format specifier `.3g` in an f-string instructs Python to format the number with 3 significant digits using general format. For `0.123456789`, the first three significant digits are '123', and the general format automatically switches to fixed-point notation when the exponent is small, producing '0.123' exactly as expected.
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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Last reviewed: Jun 24, 2026
This PCAP 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 PCAP exam.
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