Pattern match

2 snippets across 2 stacks — Python, SQL

Also written as match patterns

PYPython

Match/Case Pattern Types

syntax

match value:
    case pattern:
        ...

example

def describe(value):
    match value:
        case int(n) if n > 0:
            return f"positive int: {n}"
        case str(s) if len(s) > 5:
            return f"long string: {s!r}"
        case [first, *rest]:
            return f"list starting with {first}, {len(rest)} more"
        case {"type": "error", "code": code}:
            return f"error code {code}"
        case _:
            return "something else"

print(describe(42))
print(describe([1, 2, 3]))
print(describe({"type": "error", "code": 500}))

output

positive int: 42
list starting with 1, 2 more
error code 500

Note Match/case supports literal, capture, sequence, mapping, class, guard (if), and OR (|) patterns. The _ wildcard matches anything.

SQLSQL

LIKE Pattern Matching

SQL · Filtering

syntax

WHERE column LIKE 'pattern'
-- % = any number of characters
-- _ = exactly one character

example

SELECT first_name, email
FROM users
WHERE email LIKE '%@gmail.com';

output

-- All users with Gmail addresses

Note LIKE is case-sensitive in PostgreSQL but case-insensitive in MySQL (with default collation). PostgreSQL offers ILIKE for case-insensitive matching. A leading % prevents index usage.