I'm trying to find a good way to split a string using a regular expression instead of a string. Thanks
http://nsf.github.io/go/strings.html?f:Split!
You can use regexp.Split to split a string into a slice of strings with the regex pattern as the delimiter.
package main
import (
"fmt"
"regexp"
)
func main() {
re := regexp.MustCompile("[0-9]+")
txt := "Have9834a908123great10891819081day!"
split := re.Split(txt, -1)
set := []string{}
for i := range split {
set = append(set, split[i])
}
fmt.Println(set) // ["Have", "a", "great", "day!"]
}
I made a regex-split function based on the behavior of regex split function in java, c#, php.... It returns only an array of strings, without the index information.
func RegSplit(text string, delimeter string) []string {
reg := regexp.MustCompile(delimeter)
indexes := reg.FindAllStringIndex(text, -1)
laststart := 0
result := make([]string, len(indexes) + 1)
for i, element := range indexes {
result[i] = text[laststart:element[0]]
laststart = element[1]
}
result[len(indexes)] = text[laststart:len(text)]
return result
}
example:
fmt.Println(RegSplit("a1b22c333d", "[0-9]+"))
result:
[a b c d]
If you just want to split on certain characters, you can use strings.FieldsFunc, otherwise I'd go with regexp.FindAllString.
The regexp.Split() function would be the best way to do this.
You should be able to create your own split function that loops over the results of RegExp.FindAllString, placing the intervening substrings into a new array.
http://nsf.github.com/go/regexp.html?m:Regexp.FindAllString!
I found this old post while looking for an answer. I'm new to Go but these answers seem overly complex for the current version of Go. The simple function below returns the same result as those above.
package main
import (
"fmt"
"regexp"
)
func goReSplit(text string, pattern string) []string {
regex := regexp.MustCompile(pattern)
result := regex.Split(text, -1)
return result
}
func main() {
fmt.Printf("%#v\n", goReSplit("Have9834a908123great10891819081day!", "[0-9]+"))
}
Related
I'm trying to build an application that reads lines of csv text from the network and inserts it into sqlite db. I need to extract all strings that appear between commas, including empty strings.
For e.g a line of text that I need to parse looks like:
"1/17/09 1:23,\"Soap, Shampoo and cleaner\",,1200,Amex,Steven O' Campbell,,Kuwait,1/16/09 14:26,1/18/09 9:08,29.2891667,,48.05"
My code snippet is below , I figured I need to use regex since I'm trying to split the line of string at "," character but the comma may also appear as part of the string.
package main
import (
"fmt"
"regexp"
"strings"
)
func main() {
re := regexp.MustCompile(`^|[^,"']+|"([^"]*)"|'([^']*)`)
txt := "1/17/09 1:23,\"Soap, Shampoo and cleaner\",,1200,Amex,Steven O' Campbell,,Kuwait,1/16/09 14:26,1/18/09 9:08,29.2891667,,48.05"
arr := re.FindAllString(txt, -1)
arr2 := strings.Split(txt, ",")
fmt.Println("Array lengths: ", len(arr), len(arr2))
}
The correct length of the split array in this case should be 13.
Like Marc and Flimzy said, regex isn't the right tool here. And since you're not specifying that we should use regex as the tool to extract data from your string, here's a snippet on how you'd extract those from your string and fit the result you're looking for:
import (
"bytes"
"encoding/csv"
"fmt"
)
func main() {
var testdata = `1/17/09 1:23,"Soap, Shampoo and cleaner",,1200,Amex,Steven O' Campbell,,Kuwait,1/16/09 14:26,1/18/09 9:08,29.2891667,,48.05`
var reader = csv.NewReader(bytes.NewBufferString(testdata))
var content, err = reader.Read()
if err != nil {
panic(err)
}
fmt.Println(len(content)) // 13
}
content := `{null,"Age":24,"Balance":33.23}`
rule,_ := regexp.Compile(`"([^\"]+)"`)
results := rule.FindAllString(content,-1)
fmt.Println(results[0]) //"Age"
fmt.Println(results[1]) //"Balance"
There is a json string with a ``null`` value that it look like this.
This json is from a web api and i don't want to replace anything inside.
I want to using regex to match all the keys in this json which are without the double quote and the output are ``Age`` and ``Balance`` but not ``"Age"`` and ``"Balance"``.
How can I achieve this?
One solution would be to use a regular expression that matches any character between quotes (such as your example or ".*?") and either put a matching group (aka "submatch") inside the quotes or return the relevant substring of the match, using regexp.FindAllStringSubmatch(...) or regexp.FindAllString(...), respectively.
For example (Go Playground):
func main() {
str := `{null,"Age":24,"Balance":33.23}`
fmt.Printf("OK1: %#v\n", getQuotedStrings1(str))
// OK1: []string{"Age", "Balance"}
fmt.Printf("OK2: %#v\n", getQuotedStrings2(str))
// OK2: []string{"Age", "Balance"}
}
var re1 = regexp.MustCompile(`"(.*?)"`) // Note the matching group (submatch).
func getQuotedStrings1(s string) []string {
ms := re1.FindAllStringSubmatch(s, -1)
ss := make([]string, len(ms))
for i, m := range ms {
ss[i] = m[1]
}
return ss
}
var re2 = regexp.MustCompile(`".*?"`)
func getQuotedStrings2(s string) []string {
ms := re2.FindAllString(s, -1)
ss := make([]string, len(ms))
for i, m := range ms {
ss[i] = m[1 : len(m)-1] // Note the substring of the match.
}
return ss
}
Note that the second version (without a submatching group) may be slightly faster based on a simple benchmark, if performance is critical.
Using Go, how do I replace all characters in a string with "X" except the last 4 characters?
This works fine for php/javascript but not for golang as "?=" is not supported.
\w(?=\w{4,}$)
Tried this, but does not work. I couldn't find anything similar for golang
(\w)(?:\w{4,}$)
JavaScript working link
Go non-working link
A simple yet efficient solution that handles multi UTF-8-byte characters is to convert the string to []rune, overwrite runes with 'X' (except the last 4), then convert back to string.
func maskLeft(s string) string {
rs := []rune(s)
for i := 0; i < len(rs)-4; i++ {
rs[i] = 'X'
}
return string(rs)
}
Testing it:
fmt.Println(maskLeft("123"))
fmt.Println(maskLeft("123456"))
fmt.Println(maskLeft("1234世界"))
fmt.Println(maskLeft("世界3456"))
Output (try it on the Go Playground):
123
XX3456
XX34世界
XX3456
Also see related question: How to replace all characters in a string in golang
Let's say inputString is the string you want to mask all the characters of (except the last four).
First get the last four characters of the string:
last4 := string(inputString[len(inputString)-4:])
Then get a string of X's which is the same length as inputString, minus 4:
re := regexp.MustCompile("\w")
maskedPart := re.ReplaceAllString(inputString[0:len(inputString)-5], "X")
Then combine maskedPart and last4 to get your result:
maskedString := strings.Join([]string{maskedPart,last4},"")
Simpler approach without regex and looping
package main
import (
"fmt"
"strings"
)
func main() {
string := "thisisarandomstring"
head := string[:len(string)-4]
tail := string[len(string)-4:]
mask := strings.Repeat("x", len(head))
fmt.Printf("%v%v", mask, tail)
}
// Output:
// xxxxxxxxxxxxxxxring
Create a Regexp with
re := regexp.MustCompile("\w{4}$")
Let's say inputString is the string you want to remove the last four characters from. Use this code to return a copy of inputString without the last 4 characters:
re.ReplaceAllString(inputString, "")
Note: if it's possible that your input string could start out with less than four characters, and you still want those characters removed since they are at the end of the string, you should instead use:
re := regexp.MustCompile("\w{0,4}$")
As stated in the title, given a situation where I have a string like so:
"somestring~200~122"
I am wanting to regex to match the numbers when the prefix "~" occurs. So I can ultimately end up with [200, 122].
Matching the prefix is necessary as I need to protect against a case where a string like the one below should not be matched
"somestring~abc200~def122"
For additional context: As stated in the title, I am using go so I am planning on using doing something like the following in order to obtain the numbers within the string:
pattern := regexp.MustCompile("regex i need help with")
numbers := pattern.FindAllString(host, -1)
You can use FindAllStringSubmatch to extract the group containing just the digits. Below is an example that finds all instances of ~ followed by numbers. It additionally converts all the matches to ints
and inserts them into a slice:
package main
import (
"fmt"
"regexp"
"strconv"
)
func main() {
host := "somestring~200~122"
pattern := regexp.MustCompile(`~(\d+)`)
numberStrings := pattern.FindAllStringSubmatch(host, -1)
numbers := make([]int, len(numberStrings))
for i, numberString := range numberStrings {
number, err := strconv.Atoi(numberString[1])
if err != nil {
panic(err)
}
numbers[i] = number
}
fmt.Println(numbers)
}
https://play.golang.org/p/09YyewtRXz
I download a multiline file from Amazon S3 in format like:
ColumnAv1 ColumnBv1 ColumnCv1 ...
ColumnAv2 ColumnBv2 ColumnCv2 ...
the file is of type byte. Then I want to parse this with regex:
matches := re.FindAllSubmatch(file,-1)
then I want to feed result row by row to function which takes []string as input (string[0] is ColumnAv1, string[1] is ColumnBv2, ...).
How should I convert result of [][][]byte to []string containing first, second, etc row? I suppose I should do it in a loop, but I cannot get this working:
for i:=0;i<len(len(matches);i++{
tmp:=myfunction(???)
}
BTW, Why does function FindAllSubmatch return [][][]byte whereas FindAllStringSubmatch return [][]string?
(Sorry I don't have right now access to my real example, so the syntax may not be proper)
It's all explained extensively in the package's documentation.
Read the parapgraph which explains :
There are 16 methods of Regexp that match a regular expression and identify the matched text. Their names are matched by this regular expression:
Find(All)?(String)?(Submatch)?(Index)?
In your case, you probably want to use FindAllStringSubmatch.
In Go, a string is just a read-only []byte.
You can choose to either keep passing []byte variables around,
or cast the []byte values to string :
var byteSlice = []byte{'F','o','o'}
var str string
str = string(byteSlice)
You can simply iterate through the bytes result as you would do for strings result using two nested loop, and just convert slice of bytes to a string in the second loop:
package main
import "fmt"
func main() {
f := [][][]byte{{{'a', 'b', 'c'}}}
for _, line := range f {
for _, match := range line { // match is a type of []byte
fmt.Println(string(match))
}
}
}
Playground