CODING CHALLENGE · N°61

PII Redactor

Medium FDESecurityCompliance

Before customer data touches a log line — or a third-party LLM — the personal bits have to go. Mask emails, SSNs, credit cards, and phone numbers with pattern matching, leaving the rest readable. It’s the redaction step that keeps you out of a compliance incident. Solve it in Python or TypeScript, with hidden tests.

The problem

Implement redact(text): replace personal data with typed placeholders, in this order — emails → [EMAIL], US SSNs (###-##-####) → [SSN], 16-digit credit cards (optionally space/dash grouped) → [CARD], and phone numbers (###-###-#### or ###.###.####) → [PHONE]. Everything else is left untouched. Return the redacted string.

EXAMPLE 1

Input text = 'mail a@b.com ssn 123-45-6789 ph 555-123-4567'

Output mail [EMAIL] ssn [SSN] ph [PHONE]

each pattern is masked with its type

CONSTRAINTS

Apply the patterns in the given order (email, SSN, card, phone) so a card isn’t mis-tagged as a phone.
Replace with the typed token ([EMAIL], [SSN], [CARD], [PHONE]) — keep the surrounding text.
Non-matching text passes through unchanged.

SOLVE IT YOURSELF

Your turn — write it

Edit the stub, hit Run (or ⌘/Ctrl + Enter), and watch the hidden tests. Stuck? the hints are right above and Reveal solution is one click away.

YOUR TASK

Implement redact(text) with four ordered regex replacements. Use word boundaries so you match whole tokens, and apply email first (its "@" is unambiguous) and card before phone (a 16-digit run must not be split into phone-shaped pieces).

HINTS — 4 IDEAS

Email: [A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,} → [EMAIL].
SSN: \b\d{3}-\d{2}-\d{4}\b → [SSN].
Card: \b\d{4}[- ]?\d{4}[- ]?\d{4}[- ]?\d{4}\b → [CARD] (before phone).
Phone: \b\d{3}[-.]\d{3}[-.]\d{4}\b → [PHONE].

CPython · WebAssembly

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