PCAP Exceptions and File I/O Practice Question

Answer analysis

Option-by-option breakdown

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

• ✗

  try: read_file() except (UnicodeDecodeError, OSError): pass

  Why it's wrong here

  Catching a tuple of UnicodeDecodeError and OSError then silently passing is dangerous because it groups two unrelated failure modes: a file that cannot be decoded versus a file that cannot be read due to a missing path or permissions. Using pass discards the exception entirely, so there is no log record to indicate why a file was skipped, which is poor operational practice. Moreover, catching OSError here is unnecessary when the goal is logically to skip only corrupt encoded files, and it could hide real I/O problems.

• ✓

  try: read_file() except UnicodeDecodeError: log.warning('Skipping file')

  Why this is correct

  This is the correct approach because it deliberately catches only UnicodeDecodeError, which is the exception raised when reading and decoding bytes containing invalid UTF-8 or another specified codec. By logging a warning and doing nothing else, the handler reports the problem while allowing the surrounding loop to move on to the next uploaded file. More specific handlers like this leave unrelated exceptions—such as OSError or file-system errors—free to propagate, preserving their diagnostic value.

• ✗

  try: read_file() except Exception: log.warning('Skipping file')

  Why it's wrong here

  Using except Exception is far too broad for this use case because it intercepts every normal runtime exception, including programming mistakes like TypeError, KeyError, or ValueError, and masks them as 'skipped file' warnings. That means a genuine bug in read_file() would be hidden behind a misleading log message, making it nearly impossible to recognize and fix the actual error. Also, a blanket-except handler can interfere with cleanup or context-manager behaviors, and it captures errors that have nothing to do with decoding user uploads.

• ✗

  try: read_file() except UnicodeEncodeError: log.warning('Skipping file')

  Why it's wrong here

  UnicodeEncodeError is raised when Unicode text is being converted into bytes—for example, during str.encode() or when writing to an output stream with a specific encoding—not when reading raw bytes and decoding them into text. Since read_file() in this context is reading a user-uploaded file, the failure point is decoding those bytes into a string, which raises UnicodeDecodeError instead. Although the two exceptions are siblings under UnicodeError, catching the encode variant would leave the actual decode failure completely unhandled, causing the program to crash.

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