Text processing of Golang functions and application methods of regular expressions

Golang is a programming language with efficiency and flexibility. In the Golang language, functions and regular expressions are both very important features. Functions are widely used for text processing, while regular expressions are widely used for searching, matching, and replacing strings.

In this article, we will explore the application of Golang functions in text processing and the basic usage of regular expressions in Golang.

1. Text processing functions

In Go language, a string is an immutable byte array. In order to handle these strings we need to use the following functions.

1. Function of strings package

The strings package is one of the standard packages provided by Golang. It contains various functions for string processing. These functions can be used to truncate, concatenate, compare, split, search strings, etc. Below are some common functions.

a. strings.TrimSpace(str string) string

This function returns the result after removing the leading and trailing spaces of the string str.

b. strings.Split(str string, sep string) []string

This function splits the string str into a string array according to the separator sep.

c. strings.Join(str_list []string, sep string) string

This function connects the string array str_list with the specified separator sep and returns a connected string.

d. strings.Contains(str string, substr string) bool

This function returns a bool type value, which is used to determine whether the string str contains the substring substr.

e. strings.Index(str string, substr string) int

This function returns a value of integer type, which is used to return the position of the substring substr in the string str.

f. strings.Replace(str string, old string, new string, n int) string

This function replaces old in string str with new, n is the number of replacements.

2. Function of strconv package

strconv package is a standard package provided by Golang for converting strings to other data types, such as integers, floating point numbers and Boolean Worth waiting. The following are several commonly used functions.

a. strconv.Atoi(str string) (int, error)

This function converts the string str to a value of type int. If the conversion fails, an error is returned.

b. strconv.ParseFloat(str string, bitSize int) (float64, error)

This function converts the string str into a float64 type value. If the conversion fails, an error is returned.

c. strconv.FormatInt(i int64, base int) string

This function converts the value i of type int64 into a string.

2. Regular expression

Regular expression is a technology based on text pattern matching. It is widely used for searching, matching and replacing strings. Golang's standard library provides the regexp package to support regular expressions.

The basic syntax of regular expressions is as follows:

^ matches the beginning of the line
$ matches the end of the line
. Matches any non-
characters

• Match the previous character 0 or more times
• Match the previous character 1 or more times
  ? Match the previous character 0 or 1 times
  d Match a numeric character
  w Match an alphabetic or numeric character
  S Match any non-empty character
  [] Match any character in a character set
  () Group matching

1. Match regular expression Formula

We can use the MatchString function in the regexp package to check whether a string matches a regular expression. For example, the following code will check if a string contains a group of 3 numbers:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    match, _ := regexp.MatchString("\d{3}", "123")
    fmt.Println(match) // true

    match, _ = regexp.MatchString("\d{3}", "12")
    fmt.Println(match) // false
}

2. Compile the regular expression

The MatchString function needs to be compiled every time it is executed Regular expressions, which can have a performance impact. Therefore, we can use the Compile function to first compile the regular expression and then use it in later code.

package main

import (
    "fmt"
    "regexp"
)

func main() {
    reg := regexp.MustCompile("\d{3}")
    match := reg.MatchString("123")
    fmt.Println(match) // true

    match = reg.MatchString("12")
    fmt.Println(match) // false
}

3. Find and Replace

The regexp package also provides the FindAllString function, which is used to search for regular expressions in a string and return all matching substrings. For example, the following code will return all substrings consisting of 3 numbers in a string:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    reg := regexp.MustCompile("\d{3}")
    str := "123a456b789c"
    result := reg.FindAllString(str, -1)
    fmt.Println(result) // [123 456 789]
}

The regexp package also provides the ReplaceAllString function, which is used to replace all subcharacters in the string that match the regular expression. string is replaced with another string. For example, the following code will replace all substrings consisting of 3 numbers in the string with XXX:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    reg := regexp.MustCompile("\d{3}")
    str := "123a456b789c"
    result := reg.ReplaceAllString(str, "XXX")
    fmt.Println(result) // XXXaXXXbXXXc
}

3. Conclusion

In text processing, the functions in the Golang language have Efficiency and flexibility. We can use these functions to perform operations such as string truncation, concatenation, comparison, splitting, and searching.

Regular expression is a technology based on text pattern matching, which is widely used to search, match and replace strings. In Golang, we can use the regexp package to support regular expressions and implement matching, search and replacement operations by compiling regular expressions, MatchString function, FindAllString function and ReplaceAllString function.

Therefore, it is very important to master Golang's text processing and regular expressions. In the process of using these functions and regular expressions, we can process string data more efficiently.

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