Assuming the following information
Name: John SohCard No: 3762 1005 1102 8868
Write the regular expression to extract the credit card number

Question

BlackTom AI · Accepted Answer

The question presents a task: write the regular expression to extract a credit card number from a string that includes a name and a card number in the format four digits, a space, four digits, a space, four digits, a space, four digits.

Option/Provided answer to evaluate: \b\d{4} \d{4} \d{4} \d{4}\b

First, examine what this pattern does step by step:
- \b asserts a word boundary, ensuring the match does not occur in the middle of a longer digit sequence.
- \d{4} matches exactly four digits.
- There are literal spaces between the groups of four digits, matching the exact format "dddd dddd dddd dddd".
- The final \b asserts another word boundary after the last four digits.

With the given input containing the card number as "3762 1005 1102 8868", the pattern correctly identifies the sequence due to the exact four-digit groups separated by single spaces and bounded by non-word characters or string edges.

Next, consider potential edge cases and typical improvements:
- If the source data might use a different separator (e.g., hyphens like 1234-5678-9012-3456) or multiple spaces, the strict literal spaces would fail to match. In that case you might use a more flexible pattern like \b(?:\d{4}[- ]?){3}\d{4}\b which allows either a space or a hyphen between groups, or optionally allows multiple spaces.
- If the card number could appear embedded in longer digit sequences (e.g., part of a longer string without boundaries), the word boundaries help prevent partial matches, but depending on the surrounding text you might also want to use lookarounds to ensure precise boundaries (for example, (?<!\d) and (?!\d) to prevent adjacent digits).
- Performance and readability: using capturing groups is unnecessary here since you only need to extract the digits; the given pattern uses non-capturing structure by default, but if you need to extract, you might place the entire pattern in a non-capturing group (?:...) or rely on the global find operation.

In the context of a short-answer evaluation, the provided regex is correct for the exact format of four-digit groups separated by single spaces, with boundaries ensuring it’s a standalone sequence. If the data can vary in separators or spacing, you would adapt the pattern accordingly to maintain accurate extraction.

Assuming the following information Name: John SohCard No: 3762 1005 1102 8868 Write the regular expression to extract the credit card number

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