Validate Email Format — Solution & ExplanationProblems / Validate Email Format / EditorialApproach

One anchored regex encodes every rule: ^[^@\s]+@[^@\s]+\.[^@\s]+$.

[^@\s]+ before the @ requires a non-empty local part with no whitespace and no extra @.

[^@\s]+\.[^@\s]+$ after the @ requires a domain containing a literal dot with characters on both sides — missing@dotcom, user@.com, and trailing@dot. all fail.

DuckDB's regexp_matches(email, pattern) returns the BOOLEAN directly; in PySpark the same test is F.col('email').rlike(pattern).

Key InsightYou never need to *count* the @ signs: because both character classes exclude @, any second occurrence (as in two@ats@example.com) has nowhere to match and the whole pattern fails. The other classic trap is anchoring — regexp_matches and rlike search for the pattern anywhere in the string, so without ^...$ an invalid address containing a valid-looking substring would slip through.Hints

Character classes that exclude @ do double duty: [^@\s]+ matches the local part AND guarantees no second @ can hide anywhere in the string.

Anchor with ^ and $ — DuckDB's regexp_matches and Spark's rlike both succeed on partial matches, so an unanchored pattern would call 'a b@c.com d' valid.

The domain rule is [^@\s]+\.[^@\s]+ — a literal (escaped) dot with at least one character on each side, which rejects 'missing@dotcom', 'user@.com' and 'trailing@dot.'.

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