Golang : Turn string or text file into slice example



Tags : golang text-string convert-to-slice delete copy append

Alright, I need to parse a large number of text files that contain some raw data generated by a machine. Below is a small program that I've created to test how to write Golang program to turn string data or text file into a slice, delete one line base on the index/key position and insert a new line of string.

The delete and insert operations can be tricky, so care must be taken to ensure that the correct data are being manipulated.

This program below only handle embedded text string data. Please read the previous tutorial on how to read a text file and convert the data into lines of slice.

Here you go!


 package main

 import (
 "fmt"
 "strings"
 )

 func main() {

 textString := `line 1
 line 2
 line 3
 line 4`

 lines := strings.Split(textString, "\n")

 for i, line := range lines {
 // i = i + 1 // uncomment to start from 1 instead of 0
 fmt.Println(i, " : ", line)
 }

 // IMPORTANT: append() function will alter the lines slice
 // therefore, let's make a copy of the original lines slice to preserve the data.
 // Use make instead of var. If you use var, the destination slice will be empty!

 originalLines := make([]string, len(lines))
 copy(originalLines, lines[:])

 // since lines is a slice, we can delete a line by index position
 indexToDelete := 2 // remember counting starts from 0
 linesAfterDelete := append(lines[:indexToDelete], lines[indexToDelete+1:]...)

 fmt.Println("=======================================================")
 // after delete
 for i, line := range linesAfterDelete {
 // i = i + 1 // uncomment to start from 1 instead of 0
 fmt.Println(i, " : ", line)
 }

 fmt.Println("=======================================================")

 fmt.Println("append() function will alter the lines slice, so make sure to keep a copy of the original slice")

 fmt.Println("[lines] : ", lines)
 fmt.Println("[original] : ", originalLines)

 // we will use originalLines slice here instead of lines

 fmt.Println("=======================================================")
 indexToInsert := 1
 stringToInsert := "Hello World!"
 linesAfterInsert := append(originalLines[:indexToInsert], stringToInsert)

 // don't forget to append the rest
 linesAfterInsert = append(linesAfterInsert[:indexToInsert+1], originalLines[indexToInsert+1:]...)

 // after insert
 for i, line := range linesAfterInsert {
 // i = i + 1 // uncomment to start from 1 instead of 0
 fmt.Println(i, " : ", line)
 }

 }

Sample output:

0 : line 1

1 : line 2

2 : line 3

3 : line 4

=======================================================

0 : line 1

1 : line 2

2 : line 4

=======================================================

append() function will alter the lines slice, so make sure to keep a copy of the original slice

[lines] : [line 1 line 2 line 4 line 4]

[original] : [line 1 line 2 line 3 line 4]

=======================================================

0 : line 1

1 : Hello World!

2 : line 3

3 : line 4

Happy coding!

References:

How to use Golang's builtin copy function example

Golang : Delete item from slice based on index/key position

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  See also : Golang : Display a text file line by line with line number example



Tags : golang text-string convert-to-slice delete copy append

By Adam Ng

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