ParseInt Examples: Convert String to Int
This page was last reviewed on Jul 6, 2023.
Dot Net Perls
ParseInt. A string in Golang can contain digit characters like "123." We can convert this string to a number (an int) with the strconv.ParseInt method.
Other options. With Atoi we have a simpler way to call ParseInt. These methods return 2 values: the parsed integer itself, and an error code.
Convert String, Bool
Example, ParseInt. Let us begin with this simple example. We import the strconv package at the top. We assign 2 values to the result of strconv.ParseInt.
Argument 1 We call ParseInt with 3 arguments—the first is the string we want to get an integer from.
Argument 2 This is the base of the string being parsed. Most numbers we use are base 10.
Argument 3 This is the bit size of the resulting int. 0 means int, while 6 (for example) means int16, with 16 bits.
package main import ( "fmt" "strconv" ) func main() { value := "123" // Convert string to int. number, _ := strconv.ParseInt(value, 10, 0) // We now have an int. fmt.Println(number) if number == 123 { fmt.Println(true) } }
123 true
Atoi. This function bears the same name as the one from the C standard library. In Go it invokes ParseInt with a base of 10 and a bit size of 0.
Tip The Atoi call here is simpler than ParseInt. This gives it an advantage in readability in programs.
package main import ( "fmt" "strconv" ) func main() { value := "456" // Use Atoi to parse string. number, _ := strconv.Atoi(value) fmt.Println(number) fmt.Println(number + 1) }
456 457
FormatInt. With this method, we convert an int to a string. This is the opposite conversion as ParseInt. With FormatInt, we must pass an int64 value—we cast in this example.
package main import ( "fmt" "strconv" ) func main() { value := 1055 // Convert int to string with FormatInt. // ... First convert to int64. result := strconv.FormatInt(int64(value), 10) fmt.Println(result) if result == "1055" { fmt.Println(true) } }
1055 true
Itoa. This method converts an int into a string. It calls FormatInt with a base of 10. It also accepts a simple int, not an int64, so less casting may be required.
Note Unlike ParseInt and Atoi, FormatInt and Itoa do not return an error value. They succeed on all possible arguments.
package main import ( "fmt" "strconv" ) func main() { value := 700 // Use Itoa on an int. result := strconv.Itoa(value) fmt.Println(result) // The string has 3 characters. fmt.Println(len(result)) }
700 3
ParseInt benchmark. Often we need to convert a string into an integer. This benchmark compares ParseInt and Atoi. It converts "1234" into an integer with each method.
Version 1 This version of the code uses the ParseInt method. It repeatedly calls ParseInt in a loop.
Version 2 Here we use the Atoi method, in a similar way as in version 1. We try to determine the time required per method call.
Result We find that the ParseInt method seems to be faster. It should be preferred when it can be used.
package main import ( "fmt" "strconv" "time" ) func main() { t0 := time.Now() original := "1234"; // Version 1: use ParseInt. for i := 0; i < 1000000; i++ { result, _ := strconv.ParseInt(original, 10, 0) if result != 1234 { return } } t1 := time.Now() // Version 2: use Atoi. for i := 0; i < 1000000; i++ { result, _ := strconv.Atoi(original) if result != 1234 { return } } t2 := time.Now() // Results of benchmark. fmt.Println(t1.Sub(t0)) fmt.Println(t2.Sub(t1)) }
14.023ms ParseInt 18.5125ms Atoi
A review. We converted strings to integers in Go. With ParseInt and the convenient method Atoi that calls ParseInt with common arguments, we perform this task with ease.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Jul 6, 2023 (edit).
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