Go language processes CSV files directly and efficiently, and the standard library encoding/csv can meet most needs. When reading, use csv.NewReader() to create a reader, and read data through ReadAll() or line by line; if the title line is included, you can skip the first line and set TrimLeadingSpace to remove spaces or Comma to replace the separator. When writing, use csv.NewWriter() to create a writer, call Write()/WriteAll() to output data. Note that the os.O_APPEND flag is required to add content and be sure to call Flush() to ensure that the data is landed. When dealing with special characters, the CSV package supports the RFC 4180 specification by default. Commas and newlines in fields need to be wrapped in quotes, and double quotes need to be escaped. When constructing CSV, unescaped special symbols should be avoided to ensure the correct format.
Processing CSV files is actually quite straightforward in Go language. encoding/csv package in the standard library can already meet most common needs. Whether it is reading or writing CSV data, it can be done easily with this package.
How to read a CSV file?
Reading CSV is one of the most common operations, such as exporting data from a database or parsing a table file uploaded by a user.
Go's csv.NewReader() method can help you create a reader and then get the data through .ReadAll() or line-by-line reading.
Let's give a simple example:
file, err := os.Open("data.csv")
if err != nil {
log.Fatal(err)
}
defer file.Close()
reader := csv.NewReader(file)
records, err := reader.ReadAll()
if err != nil {
log.Fatal(err)
} The above code will read the entire CSV file into the two-dimensional string slice of records at one time. Each row is an array of strings corresponding to a column of data.
Tips:
- If your CSV file has a header, you can skip the first line after reading it.
- You can set
reader.Comma = '\t'to read the TSV file. - Use
reader.TrimLeadingSpace = trueto automatically remove spaces before the field.
How to write to a CSV file?
Writing to CSV is just as simple as creating a writer using csv.NewWriter() and then calling .Write() or .WriteAll() methods.
For example, generate a CSV file with several records:
file, _ := os.Create("output.csv")
writer := csv.NewWriter(file)
defer writer.Flush()
headers := []string{"Name", "Age", "City"}
data := [][]string{
{"Alice", "30", "New York"},
{"Bob", "25", "San Francisco"},
}
writer.Write(headers)
for _, record := range data {
writer.Write(record)
}This will generate a CSV file with header and two rows of data.
Note:
- Remember to call
.Flush()after writing the data, otherwise the data may not be written in. - If you want to append content instead of overwriting, you can use
os.OpenFileand add theos.O_APPENDflag.
How to deal with special characters or formats in CSV?
CSV looks simple, but what you actually encounter may not be that clean. For example, if there are commas, line breaks or quotes in the field, the default parsing method may be incorrect at this time.
Go's CSV package supports RFC 4180 format by default, that is:
- The commas in the field are correctly recognized as delimiters;
- When a newline appears in a field, the field should be wrapped in double quotes;
- Double quotes themselves need to be escaped, i.e. two consecutive double quotes represent one.
So as long as your input is based on this specification, there will generally be no problem.
If you construct CSV data yourself, it is also recommended to avoid unescaped commas or newlines in the fields. If it is really impossible to avoid it, be sure to wrap the field in double quotes and escape the internal quotes.
Basically that's it. Go handles CSVs very practical and does not require additional dependence on third-party libraries. As long as you master ReadAll , Write and some format precautions, you can deal with most scenarios.
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