27 · Biblioteca Padrão
CSV (std::csv)
Parsear e serializar CSV: linhas, cabeçalhos, escaping de aspas e round-trip.
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std::csv lê e produz texto CSV. Cada linha vira um array de campos;
parse_with_headers devolve mapas keyed pelo cabeçalho.
Parse
csv.parse(string) retorna um array de arrays — a primeira linha é tratada
como qualquer outra. csv.parse_with_headers usa a primeira linha como chaves:
Acesso por índice com parse e por nome com parse_with_headers.
// Feature: csv.parse — parses CSV into an array of arrays
// When to use: import spreadsheets, read CSV-formatted logs.
use std::csv
// Each line becomes an array; the result is an array of rows.
let raw = "name,age,active\nAlice,30,true\nBob,25,false"
let rows = csv.parse(raw)
print(rows[0][0]) // expected: name (header)
print(rows[0][1]) // expected: age
print(rows[1][0]) // expected: Alice
print(rows[2][1]) // expected: 25
// With header: parse_with_headers returns an array of maps.
let people = csv.parse_with_headers(raw)
print(people[0]["name"]) // expected: Alice
print(people[0]["age"]) // expected: 30
print(people[1]["active"]) // expected: false
Escaping de Campos Especiais
Campos com vírgulas devem estar entre aspas no CSV; aspas internas são
duplicadas (""). O parser lida com esses casos automaticamente:
Endereços com vírgula, aspas aninhadas e campos vazios.
// Feature: csv.parse — fields with quotes, commas, and line breaks
// When to use: user data may contain special characters — double quotes
// escape inner quotes, and fields containing commas must be quoted.
use std::csv
// A field containing a comma must be quoted.
let raw1 = "name,address\nAlice,\"100 Main St, Apt 1\"\nBob,\"200 Oak Ave, Apt 2\""
let rows = csv.parse(raw1)
print(rows[1][1]) // expected: 100 Main St, Apt 1
print(rows[2][1]) // expected: 200 Oak Ave, Apt 2
// Double quotes inside a field: use "" to escape.
let raw2 = "msg\n\"she said \"\"hi\"\" yesterday\""
let rows2 = csv.parse(raw2)
print(rows2[1][0]) // expected: she said "hi" yesterday
// Empty fields become empty strings.
let raw3 = "a,b,c\n1,,3"
let rows3 = csv.parse(raw3)
print(rows3[1][1]) // expected: (empty)
Stringify
csv.stringify(linhas) serializa um array de arrays em texto CSV, colocando
aspas automaticamente quando o campo contém vírgulas:
Round-trip: stringify → parse preserva campos com vírgula.
// Feature: csv.stringify — serializes an array of arrays into CSV
// When to use: export data to a spreadsheet, generate reports.
use std::csv
let rows = [
["name", "age", "city"],
["Alice", "30", "New York"],
["Bob", "25", "Austin, TX"], // comma in field: csv quotes it automatically
["Carol", "40", "San Francisco"],
]
let out = csv.stringify(rows)
print(out)
// expected:
// name,age,city
// Alice,30,New York
// Bob,25,"Austin, TX"
// Carol,40,San Francisco
// Round-trip: stringify -> parse returns the same structure.
let parsed = csv.parse(out)
print(parsed[2][2]) // expected: Austin, TX
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