Courseiva
← PCAP
Full test
Exceptions and File I/O →mediumMultiple Choice

PCAP Exceptions and File I/O Practice Question

Exhibit

{
  "logging": {
    "level": "DEBUG",
    "file": "/var/log/app.log"
  },
  "database": {
    "host": "localhost",
    "port": 5432
  }
}

Refer to the exhibit. A developer is writing a script to read this JSON configuration file. The script should write the logging configuration to a separate file called 'logging.conf'. Which file mode should be used to create the file if it doesn't exist, and overwrite it if it does?

⚠ Common exam trap

Python Institute often tests the distinction between 'w' and 'x' modes, where candidates mistakenly choose 'x' thinking it creates a new file, forgetting that 'x' raises an error if the file already exists, thus failing the overwrite requirement.

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

✓

'w'

('w') is correct because the 'w' mode opens a file for writing, truncating it first if it exists, and creating it if it does not. This matches the requirement to overwrite an existing 'logging.conf' file or create a new one if absent.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    'x'

    Why it's wrong here

    Mode 'x' stands for exclusive creation: it attempts to create a new file for writing but immediately raises FileExistsError if the given path already exists. Because the script likely expects to overwrite an existing file (or create it if missing), this mode would abort the operation instead of truncating and rewriting the content, making it incorrect for the intended behavior.

  • ✗

    'r+'

    Why it's wrong here

    Mode 'r+' opens the file for both reading and writing without truncating it, and it raises FileNotFoundError if the file does not exist. Since this mode never creates a missing file, it cannot fulfill a requirement to write to a fresh output, and any writes overwrite bytes at the current file position, leaving leftover trailing data from longer prior content rather than producing a clean result.

  • ✗

    'a'

    Why it's wrong here

    Mode 'a' opens the file for appending, positioning the file pointer at the end so that all writes go to the end regardless of seek positions, and it never truncates existing content. Using 'a' would cause new data to accumulate after any prior contents, resulting in a file that mixes old and new output, which is not a clean replacement of the file's contents.

  • ✓

    'w'

    Why this is correct

    Mode 'w' opens the file for writing, creating the file if it does not exist and truncating it to zero length if it does, thereby discarding all previous contents. This exactly matches the need to write a complete, fresh set of data: any existing content is erased before the first write, ensuring that the final file contains only the current output with no stale data.

About these practice questions

Courseiva writes every PCAP question from scratch — 421 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →

How Courseiva writes practice questions · Editorial policy

Same concept, more angles

1 more way this is tested on PCAP

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. Which TWO of the following file modes will create a new file if it doesn't exist? (Select exactly 2)

easy
  • ✓ A.'x'
  • ✓ B.'a'
  • C.'rb'
  • D.'w'
  • E.'r'

Why A: Option A, the 'x' mode, is correct because it is the exclusive creation mode: open() with 'x' creates a new file and raises FileExistsError if the file already exists, so it always creates the file when it is absent. Option B, the 'a' mode, is correct because append mode opens the file for writing at the end and creates the file if it does not already exist. Option C, 'rb', is incorrect because it opens an existing file in read-only binary mode and raises FileNotFoundError rather than creating anything. Option D, 'w', is not among the marked answers, and Option E, 'r', is incorrect because read mode requires the file to already exist and does not create it.

JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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.