langref.org - python, csharp, java, and fsharp - Regex

Replace the first regex match in a string with a static string

Transform "Red Green Blue" into "R*d Green Blue" by replacing /e/ with "*"

python

print re.sub(r'e', '*', 'Red Green Blue', 1)

java

String replaced = "Red Green Blue".replaceFirst("e", "*");

fsharp

let replaced = ((new Regex("e")).Replace("Red Green Blue", "*", 1))
printfn "%s" replaced

Replace all regex matches in a string with a static string

Transform "She sells sea shells" into "She X X shells" by replacing /se\w+/ with "X"

python

transformed = re.sub(r'se\w+', 'X', 'She sells sea shells')

csharp

using System.Text.RegularExpressions;

class SolutionXX
{
static void Main()
{
string text = "She sells sea shells";
string result = Regex.Replace(text, @"se\w+", "X");
}
}

java

String replaced = text.replaceAll("se\\w+", "X");

fsharp

let replaced = ((new Regex("se\\w+")).Replace("She sells sea shells", "X"))
printfn "%s" replaced

Replace all regex matches in a string with a dynamic string

Transform "The {Quick} Brown {Fox}" into "The kciuQ Brown xoF" by reversing words in braces using the regex /\{(\w+)\}/.

python

transformed = re.sub(r'\{(\w+)\}',
lambda match: match.group(1)[::-1],
'The {Quick} Brown {Fox}')

java

Matcher m = Pattern.compile("\\{(\\w+)\\}").matcher("The {Quick} Brown {Fox}");
StringBuffer sb = new StringBuffer(32), rsb = new StringBuffer(8);

while (m.find())
{
rsb.replace(0, rsb.length(), m.group(1)); rsb.reverse(); m.appendReplacement(sb, rsb.toString());
}
m.appendTail(sb);

fsharp

open System
open System.Text.RegularExpressions
let reverseMatch (m:Match) =
String(m.Groups.[1].Value.ToCharArray() |> Array.rev)
let output = Regex.Replace("The {Quick} Brown {Fox}", @"\{(\w+)\}", reverseMatch)