Golang，有没有更好的方法将一个整数文件读入数组中？

huangapple
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英文:

Golang, is there a better way read a file of integers into an array?

问题

我需要将一个包含整数的文件读入到一个数组中。我已经用以下代码实现了这个功能：

  1. package main
  3. import (
  4.     "fmt"
  5.     "io"
  6.     "os"
  7. )
  9. func readFile(filePath string) (numbers []int) {
  10.     fd, err := os.Open(filePath)
  11.     if err != nil {
  12.         panic(fmt.Sprintf("open %s: %v", filePath, err))
  13.     }
  14.     var line int
  15.     for {
  17.         _, err := fmt.Fscanf(fd, "%d\n", &line)
  19.         if err != nil {
  20.             fmt.Println(err)
  21.             if err == io.EOF {
  22.                 return
  23.             }
  24.             panic(fmt.Sprintf("Scan Failed %s: %v", filePath, err))
  26.         }
  27.         numbers = append(numbers, line)
  28.     }
  29.     return
  30. }
  32. func main() {
  33.     numbers := readFile("numbers.txt")
  34.     fmt.Println(len(numbers))
  35. }

文件 numbers.txt 的内容如下：

  1. 1
  2. 2
  3. 3
  4. ...

ReadFile() 函数看起来有点长（可能是因为错误处理的原因）。

有没有更短、更符合 Go 语言习惯的方法来加载一个文件？

英文:

I need to read a file of integers into an array. I have it working with this:

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"io"
  6. 	"os"
  7. )
  9. func readFile(filePath string) (numbers []int) {
  10. 	fd, err := os.Open(filePath)
  11. 	if err != nil {
  12. 		panic(fmt.Sprintf("open %s: %v", filePath, err))
  13. 	}
  14. 	var line int
  15. 	for {
  17. 		_, err := fmt.Fscanf(fd, "%d\n", &line)
  19. 		if err != nil {
  20. 			fmt.Println(err)
  21. 			if err == io.EOF {
  22. 				return
  23. 			}
  24. 			panic(fmt.Sprintf("Scan Failed %s: %v", filePath, err))
  26. 		}
  27. 		numbers = append(numbers, line)
  28. 	}
  29. 	return
  30. }
  32. func main() {
  33. 	numbers := readFile("numbers.txt")
  34. 	fmt.Println(len(numbers))
  35. }

The file numbers.txt is just:

  1. 1
  2. 2
  3. 3
  4. ...

ReadFile() seems too long (maybe because of the error handing).

Is there a shorter / more Go idiomatic way to load a file?

答案1

得分: 25

使用bufio.Scanner很方便。我还使用了io.Reader而不是使用文件名。通常这是一个很好的技巧，因为它允许代码在_任何_类似文件的对象上使用，而不仅仅是磁盘上的文件。这里它从一个字符串中“读取”。

  1. package main
  3. import (
  4. 	"bufio"
  5. 	"fmt"
  6. 	"io"
  7. 	"strconv"
  8. 	"strings"
  9. )
  11. // ReadInts从r中读取以空格分隔的整数。如果有错误，它会返回到目前为止成功读取的整数以及错误值。
  12. func ReadInts(r io.Reader) ([]int, error) {
  13. 	scanner := bufio.NewScanner(r)
  14. 	scanner.Split(bufio.ScanWords)
  15. 	var result []int
  16. 	for scanner.Scan() {
  17. 		x, err := strconv.Atoi(scanner.Text())
  18. 		if err != nil {
  19. 			return result, err
  20. 		}
  21. 		result = append(result, x)
  22. 	}
  23. 	return result, scanner.Err()
  24. }
  26. func main() {
  27. 	tf := "1\n2\n3\n4\n5\n6"
  28. 	ints, err := ReadInts(strings.NewReader(tf))
  29. 	fmt.Println(ints, err)
  30. }
英文:

Using a bufio.Scanner makes things nice. I've also used an io.Reader rather than taking a filename. Often that's a good technique, since it allows the code to be used on any file-like object and not just a file on disk. Here it's "reading" from a string.

  1. package main
  3. import (
  4. 	"bufio"
  5. 	"fmt"
  6. 	"io"
  7. 	"strconv"
  8. 	"strings"
  9. )
  11. // ReadInts reads whitespace-separated ints from r. If there's an error, it
  12. // returns the ints successfully read so far as well as the error value.
  13. func ReadInts(r io.Reader) ([]int, error) {
  14. 	scanner := bufio.NewScanner(r)
  15. 	scanner.Split(bufio.ScanWords)
  16. 	var result []int
  17. 	for scanner.Scan() {
  18. 		x, err := strconv.Atoi(scanner.Text())
  19. 		if err != nil {
  20. 			return result, err
  21. 		}
  22. 		result = append(result, x)
  23. 	}
  24. 	return result, scanner.Err()
  25. }
  27. func main() {
  28. 	tf := "1\n2\n3\n4\n5\n6"
  29. 	ints, err := ReadInts(strings.NewReader(tf))
  30. 	fmt.Println(ints, err)
  31. }

答案2

得分: 5

我会这样做：

  1. package main
  3. import (
  4. "fmt"
  5.     "io/ioutil"
  6.     "strconv"
  7.     "strings"
  8. )
  10. // 最好让这样的函数返回错误，而不是自己处理错误。
  11. func readFile(fname string) (nums []int, err error) {
  12.     b, err := ioutil.ReadFile(fname)
  13.     if err != nil { return nil, err }
  15.     lines := strings.Split(string(b), "\n")
  16.     // 为了避免每次追加都重新分配内存，给切片分配容量。
  17.     nums = make([]int, 0, len(lines))
  19.     for _, l := range lines {
  20.         // 当使用Split时，文件末尾会出现空行。
  21.         if len(l) == 0 { continue }
  22.         // 当我们确切知道要处理的内容时，Atoi更适合这个任务。Scanf是更通用的选项。
  23.         n, err := strconv.Atoi(l)
  24.         if err != nil { return nil, err }
  25.         nums = append(nums, n)
  26.     }
  28.     return nums, nil
  29. }
  31. func main() {
  32.     nums, err := readFile("numbers.txt")
  33.     if err != nil { panic(err) }
  34.     fmt.Println(len(nums))
  35. }
英文:

I would do it like this:

  1. package main
  3. import (
  4. "fmt"
  5.     "io/ioutil"
  6.     "strconv"
  7.     "strings"
  8. )
  10. // It would be better for such a function to return error, instead of handling
  11. // it on their own.
  12. func readFile(fname string) (nums []int, err error) {
  13.     b, err := ioutil.ReadFile(fname)
  14.     if err != nil { return nil, err }
  16.     lines := strings.Split(string(b), "\n")
  17.     // Assign cap to avoid resize on every append.
  18.     nums = make([]int, 0, len(lines))
  20.     for _, l := range lines {
  21.         // Empty line occurs at the end of the file when we use Split.
  22.         if len(l) == 0 { continue }
  23.         // Atoi better suits the job when we know exactly what we're dealing
  24.         // with. Scanf is the more general option.
  25.         n, err := strconv.Atoi(l)
  26.         if err != nil { return nil, err }
  27.         nums = append(nums, n)
  28.     }
  30.     return nums, nil
  31. }
  33. func main() {
  34.     nums, err := readFile("numbers.txt")
  35.     if err != nil { panic(err) }
  36.     fmt.Println(len(nums))
  37. }

答案3

得分: 0

你使用 fmt.Fscanf 的解决方案是可以的。根据你的情况，当然还有其他几种方法可以实现。Mostafa 的技巧是我经常使用的一种（尽管我可能会使用 make 一次性分配结果。哎呀！划掉。他确实这样做了。），但是为了最大的控制力，你应该学习 bufio.ReadLine。请参考 https://stackoverflow.com/questions/6141604/go-readline-string 上的一些示例代码。

英文:

Your solution with fmt.Fscanf is fine. There are certainly a number of other ways to do though, depending on your situation. Mostafa's technique is one I use a lot (although I might allocate the result all at once with make. oops! scratch that. He did.) but for ultimate control you should learn bufio.ReadLine. See https://stackoverflow.com/questions/6141604/go-readline-string for some example code.

huangapple
  • 本文由 发表于 2012年3月26日 01:41:54
  • 转载请务必保留本文链接：https://go.coder-hub.com/9862443.html
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