How to remove lines that started with certain substring in []byte, in Ruby usually I do something like this:
lines = lines.split("\n").reject{|r| r.include? 'substring'}.join("\n")
How to do this on Go?
You could emulate that with regexp:
re := regexp.MustCompile("(?m)[\r\n]+^.*substring.*$")
res := re.ReplaceAllString(s, "")
(The OP Kokizzu went with "(?m)^.*" +substr+ ".*$[\r\n]+")
See this example
func main() {
s := `aaaaa
bbbb
cc substring ddd
eeee
ffff`
re := regexp.MustCompile("(?m)[\r\n]+^.*substring.*$")
res := re.ReplaceAllString(s, "")
fmt.Println(res)
}
output:
aaaaa
bbbb
eeee
ffff
Note the use of regexp flag (?m):
multi-line mode: ^ and $ match begin/end line in addition to begin/end text (default false)
I believe using the bytes package for this task is better than using regexp.
package main
import (
"fmt"
"bytes"
)
func main() {
myString := []byte("aaaa\nsubstring\nbbbb")
lines := bytes.Replace(myString, []byte("substring\n"), []byte(""), 1)
fmt.Println(string(lines)) // Convert the bytes to string for printing
}
Output:
aaaa
bbbb
Try it here.
The question title does not have the same meaning as the way the original question was worded. The Regex provided as the accepted solution did not solve for the use case I had of removing a whole line when finding a matching substring, like the question title indicates.
In order to remove lines that contain certain substrings in Go (title of the question), you could implement something in Go very similar to the Ruby code that Kokizzu wrote initially.
func removeLinesContainingAny(input string, toRemove []string) string {
if !strings.HasSuffix(input, "\n") {
input += "\n"
}
lines := strings.Split(input, "\n")
for i, line := range lines {
for _, rm := range toRemove {
if strings.Contains(line, rm) {
lines = append(lines[:i], lines[i+1:]...)
}
}
}
input = strings.Join(lines, "\n")
input = strings.TrimSpace(input)
input += "\n"
return input
}
See test cases here: https://go.dev/play/p/K-biYIO1kjk
In particular, you need to ensure there is a new line at the end of the input string, otherwise you will get a panic for slice bounds out of range in certain cases.
This approved solution will not work when you need to remove the top line :
func main() {
s := `aaaaa substring
bbbb
cc substring ddd
eeee
ffff`
re := regexp.MustCompile("(?m)[\r\n]+^.*substring.*$")`enter code here`
res := re.ReplaceAllString(s, "")
fmt.Println(res)
}
Related
I can use the below code to search if the text str contains any or both of the keys, i.e.if it contains "MS" or "dynamics" or both of them
package main
import (
"fmt"
"regexp"
)
func main() {
keys := []string{"MS", "dynamics"}
keysReg := fmt.Sprintf("(%s %s)|%s|%s", keys[0], keys[1], keys[0], keys[1]) // => "(MS dynamics)|MS|dynamics"
fmt.Println(keysReg)
str := "What is MS dynamics, is it a product from MS?"
re := regexp.MustCompile(`(?i)` + keysReg)
matches := re.FindAllString(str, -1)
fmt.Println("We found", len(matches), "matches, that are:", matches)
}
I want the user to enter his phrase, so I trim unwanted words and characters, then doing the search as per above.
Let's say the user input was: This,is,a,delimited,string and I need to build the keys variable dynamically to be (delimited string)|delimited|string so that I can search for my variable str for all the matches, so I wrote the below:
s := "This,is,a,delimited,string"
t := regexp.MustCompile(`(?i),|\.|this|is|a`) // backticks are used here to contain the expression, (?i) for case insensetive
v := t.Split(s, -1)
fmt.Println(len(v))
fmt.Println(v)
But I got the output as:
8
[ delimited string]
What is the wrong part in my cleaning of the input text, I'm expecting the output to be:
2
[delimited string]
Here is my playground
To quote the famous quip from Jamie Zawinski,
Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.
Two things:
Instead of trying to weed out garbage from the string ("cleaning" it), extract complete words from it instead.
Unicode is a compilcated matter; so even after you have succeeded with extracting words, you have to make sure your words are properly "escaped" to not contain any characters which might be interpreted as RE syntax before building a regexp of them.
package main
import (
"errors"
"fmt"
"regexp"
"strings"
)
func build(words ...string) (*regexp.Regexp, error) {
var sb strings.Builder
switch len(words) {
case 0:
return nil, errors.New("empty input")
case 1:
return regexp.Compile(regexp.QuoteMeta(words[0]))
}
quoted := make([]string, len(words))
for i, w := range words {
quoted[i] = regexp.QuoteMeta(w)
}
sb.WriteByte('(')
for i, w := range quoted {
if i > 0 {
sb.WriteByte('\x20')
}
sb.WriteString(w)
}
sb.WriteString(`)|`)
for i, w := range quoted {
if i > 0 {
sb.WriteByte('|')
}
sb.WriteString(w)
}
return regexp.Compile(sb.String())
}
var words = regexp.MustCompile(`\pL+`)
func main() {
allWords := words.FindAllString("\tThis\v\x20\x20,\t\tis\t\t,?a!,¿delimited?,string‽", -1)
re, err := build(allWords...)
if err != nil {
panic(err)
}
fmt.Println(re)
}
Further reading:
https://pkg.go.dev/regexp/syntax
https://pkg.go.dev/regexp#QuoteMeta
https://pkg.go.dev/unicode#pkg-variables and https://pkg.go.dev/unicode#Categories
This is a multiple choice question example. I want to get the chinese text like "英国、法国", "加拿大、墨西哥", "葡萄牙、加拿大", "墨西哥、德国" in the content of following code in golang, but it does not work.
package main
import (
"fmt"
"regexp"
"testing"
)
func TestRegex(t *testing.T) {
text := `（ B ）38.目前，亚马逊美国站后台，除了有美国站点外，还有( )站点。
A.英国、法国B.加拿大、墨西哥
C.葡萄牙、加拿大D.墨西哥、德国
`
fmt.Printf("%q\n", regexp.MustCompile(`[A-E]\.(\S+)?`).FindAllStringSubmatch(text, -1))
fmt.Printf("%q\n", regexp.MustCompile(`[A-E]\.`).Split(text, -1))
}
text:
（ B ）38.目前，亚马逊美国站后台，除了有美国站点外，还有( )站点。
A.英国、法国B.加拿大、墨西哥
C.葡萄牙、加拿大D.墨西哥、德国
pattern: [A-E]\.(\S+)?
Actual result: [["A.英国、法国B.加拿大、墨西哥" "英国、法国B.加拿大、墨西哥"] ["C.葡萄牙、加拿大D.墨西哥、德国" "葡萄牙、加拿大D.墨西哥、德国"]].
Expect result: [["A.英国、法国" "英国、法国"] ["B.加拿大、墨西哥" "加拿大、墨西哥"] ["C.葡萄牙、加拿大" "葡萄牙、加拿大"] ["D.墨西哥、德国" "墨西哥、德国"]]
I think it might be a greedy mode problem. Because in my code, it reads option A and option B as one option directly.
Non-greedy matching won't solve this, you need positive lookahead, which re2 doesn't support.
As a workaround can just search on the labels and extract the text in between manually.
re := regexp.MustCompile(`[A-E]\.`)
res := re.FindAllStringIndex(text, -1)
results := make([][]string, len(res))
for i, m := range res {
if i < len(res)-1 {
results[i] = []string{text[m[0]:m[1]], text[m[1]:res[i+1][0]]}
} else {
results[i] = []string{text[m[0]:m[1]], text[m[1]:]}
}
}
fmt.Printf("%q\n", results)
Should print
[["A." "英国、法国"] ["B." "加拿大、墨西哥\n"] ["C." "葡萄牙、加拿大"] ["D." "墨西哥、德国\n"]]
write now i have a huge string which i get from 250-300 characters and i'm writing to file using
file, err := ioutil.TempFile("/Downloads", "*.txt")
if err != nil {
log.Fatal(err)
}
file.Write(mystring)
This writes everything in one line, but is there a way to pad the lines so that automatically after 76 char, we get onto new line.
found a solution which does exactly the above requirment.
made it a generic solution to split based on "n" length and whatever delimeter is required.
you can try it in the playground if you wish (https://play.golang.org/p/5ZHCC_Z5uqc)
func insertNth(s string, n int) string {
var buffer bytes.Buffer
var n_1 = n - 1
var l_1 = len(s) - 1
for i, rune := range s {
buffer.WriteRune(rune)
if i%n == n_1 && i != l_1 {
buffer.WriteRune('\n')
}
}
return buffer.String()
}
https://play.golang.org/p/5ZHCC_Z5uqc
Did some digging in and actually found it not that difficult, posted my solution above.
Let's say I have a string called varString.
varString := "Bob,Mark,"
QUESTION: How to remove the last letter from the string? In my case, it's the second comma.
How to remove the last letter from the string?
In Go, character strings are UTF-8 encoded. Unicode UTF-8 is a variable-length character encoding which uses one to four bytes per Unicode character (code point).
For example,
package main
import (
"fmt"
"unicode/utf8"
)
func trimLastChar(s string) string {
r, size := utf8.DecodeLastRuneInString(s)
if r == utf8.RuneError && (size == 0 || size == 1) {
size = 0
}
return s[:len(s)-size]
}
func main() {
s := "Bob,Mark,"
fmt.Println(s)
s = trimLastChar(s)
fmt.Println(s)
}
Playground: https://play.golang.org/p/qyVYrjmBoVc
Output:
Bob,Mark,
Bob,Mark
Here's a much simpler method that works for unicode strings too:
func removeLastRune(s string) string {
r := []rune(s)
return string(r[:len(r)-1])
}
Playground link: https://play.golang.org/p/ezsGUEz0F-D
Something like this:
s := "Bob,Mark,"
s = s[:len(s)-1]
Note that this does not work if the last character is not represented by just one byte.
newStr := strings.TrimRightFunc(str, func(r rune) bool {
return !unicode.IsLetter(r) // or any other validation can go here
})
This will trim anything that isn't a letter on the right hand side.
I need to slice a string in Go. Possible values can contain Latin chars and/or Arabic/Chinese chars. In the following example, the slice annotation [:1] for the Arabic string alphabet is returning a non-expected value/character.
package main
import "fmt"
func main() {
a := "a"
fmt.Println(a[:1]) // works
b := "ذ"
fmt.Println(b[:1]) // does not work
fmt.Println(b[:2]) // works
fmt.Println(len(a) == len(b)) // false
}
http://play.golang.org/p/R-JxaxbfNL
First of all, you should really read about strings, bytes and runes in Go.
And here is how you can achieve what you want: Go playground (I was not able to properly paste arabic symbols, but if Chinese works, arabic should work too).
s := "abcdefghijklmnop"
fmt.Println(s[2:9])
s = "维基百科:关于中文维基百科"
fmt.Println(string([]rune(s)[2:9]))
The output is:
cdefghi
百科:关于中文
You can use the utf8string package:
package main
import "golang.org/x/exp/utf8string"
func main() {
a := utf8string.NewString("🎈🎄🎀🎢👓")
// example 1
r := a.At(1)
// example 2
s := a.Slice(1, 3)
// example 3
n := a.RuneCount()
// print
println(r == '🎄', s == "🎄🎀", n == 5)
}
https://pkg.go.dev/golang.org/x/exp/utf8string