Reading a csv into go

The general approach for reading a csv into Go is to:

1. Open a file;
2. Create a new *csv.Reader object;
3. Read the file in

This can basically be accomplished like this:

p := "my_csv.csv"
 
f, err := os.Open(p)
 
//handle error
 
defer f.Close()
 
reader := csv.NewReader(f)
 

There are two approaches at this point. The first is to use the ReadAll() method to read everything in at once as a [][]string:

data := reader.ReadAll()

This works pretty well if the csv doesn’t have headers.

Another approach is to loop over each row of the csv, which is better if the csv does have headers that we need to process.

Reading Data in as []map[string]string:

If we want to read the contents of a csv in as []map[string]string (a slice of maps), where the headers are the keys in our map, we can do this as follows:

p := "my_csv.csv"
 
f, err := os.Open(p)
 
//handle error
 
defer f.Close()
 
reader := csv.NewReader(f)
 
//read in just the first row as headers
headers, err := reader.Read()
//nb that the internal cursor is now positioned at the 2nd row of the csv
 
//handle error
 
var data []map[string]string
 
for {
	row, err := reader.Read()
	
	if err == io.EOF {
		break
	}
 
	//handle not end-of-file error
 
	if len(row) != len(headers) {
		fmt.Println("Skipping row with incorrect number of fields")	
		continue
	}
	
	d := make(map[string]string, len(headers))
 
	for i := range headers {
		d[headers[i]] = row[i]	
	}
	
	data = append(data, d)
}