Cookbooks
Go
Chapter 10. Data Formats and Serialization
Working with CSV

Go:
Working with CSV

How to:

Working with CSV files in Go is straightforward, thanks to its standard library, encoding/csv. Below is a primer on reading and writing CSV files.

Reading a CSV File

To read from a CSV file, you first open the file using os.Open, then create a new CSV reader with csv.NewReader.

package main

import (
    "encoding/csv"
    "fmt"
    "os"
)

func main() {
    file, err := os.Open("data.csv")
    if err != nil {
        panic(err)
    }
    defer file.Close()

    reader := csv.NewReader(file)
    records, err := reader.ReadAll()
    if err != nil {
        panic(err)
    }

    for _, record := range records {
        fmt.Println(record)
    }
}

This code snippet will read all records from data.csv and print them. Each record is a slice of fields.

Writing to a CSV File

For writing, you use csv.NewWriter and writer.WriteAll or writer.Write for writing multiple or single CSV records, respectively.

package main

import (
    "encoding/csv"
    "os"
)

func main() {
    file, err := os.Create("output.csv")
    if err != nil {
        panic(err)
    }
    defer file.Close()

    writer := csv.NewWriter(file)
    defer writer.Flush()

    records := [][]string{
        {"Name", "Age", "City"},
        {"John Doe", "30", "New York"},
        {"Jane Doe", "27", "Los Angeles"},
    }

    if err := writer.WriteAll(records); err != nil {
        panic(err)
    }
}

This will create a file named output.csv with the provided records. Always remember to flush the writer to ensure all buffered data is written to the file.

Deep Dive

The Go encoding/csv package provides robust support for reading and writing CSV files but it’s designed with simplicity in mind, which means it doesn’t handle more complex scenarios such as auto-detection of delimiters, dealing with quotes or embedded line breaks in fields without manual handling.

Historically, CSV handling in programming languages has often been cumbersome due to these complexities, but Go’s standard library abstracts many of these issues, allowing developers to work with CSV data with relative ease. However, for more complex CSV manipulation, third-party libraries like gocsv or handling the parsing manually may be necessary.

One notable aspect of Go’s csv package is its support for specifying custom comma (delimiter), which allows it to work seamlessly with variants of CSV files, like tab-separated values (TSV). However, when dealing with highly irregular or non-standard CSV files, Go programmers might find themselves needing to extend the existing csv reader or writer implementations.

While Go’s CSV handling capabilities are robust for general purposes, for applications requiring intensive data manipulation, such as data science or complex data transformation tasks, programmers might look into dedicated data processing packages or even other languages better suited to these tasks, like Python with its pandas library. Nonetheless, for straightforward CSV read-write operations, Go’s standard library stands out for its efficiency and simplicity.

Working with JSON