How to remove numbers from string using Regex.Replace?

Question

I need to use Regex.Replace to remove all numbers and signs from a string.

Example input: 123- abcd33
Example output: abcd

you also want the "- " removed? Those are not numbers... – jle Nov 01 '09 at 14:23 — jle, Nov 01 '09 at 14:23

score 161 · Accepted Answer · answered Nov 01 '09 at 14:23

161

Try the following:

var output = Regex.Replace(input, @"[\d-]", string.Empty);

The \d identifier simply matches any digit character.

answered Nov 01 '09 at 14:23

Noldorin

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What is the purpose of the dash? I know it's used for ranges, but there's nothing at the right? – Aaron Franke Jun 01 '22 at 20:55
Purpose is to remove it together with numbers. See input/output example in question. – volkit Dec 06 '22 at 14:04

score 26 · Answer 2 · answered Nov 01 '09 at 14:54

26

You can do it with a LINQ like solution instead of a regular expression:

string input = "123- abcd33";
string chars = new String(input.Where(c => c != '-' && (c < '0' || c > '9')).ToArray());

A quick performance test shows that this is about five times faster than using a regular expression.

answered Nov 01 '09 at 14:54

Guffa

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@SirDemon: Yes, LINQ is usually not the fastest option, but regular expressions have a bigger initial overhead. For operations on short strings setting up the RegEx object takes longer than the actual work. – Guffa Nov 01 '09 at 16:23
@Guffa Do you know how this scales? Lets say on 50k records should I go for RegEx? – Arnold Wiersma Feb 15 '16 at 13:53
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@ArnoldWiersma: Either should scale pretty well, they are both basically linear, so there are no nasty surprises. I can't tell off hand which would be faster, you would have to test that. – Guffa Feb 15 '16 at 21:57
6

alternatively `new string(text.Where(char.IsLetter).ToArray());` – Skorunka František May 10 '18 at 11:18
@SkorunkaFrantišek, the problem here is that this also trims the string – Uke Feb 14 '21 at 15:40

score 11 · Answer 3 · answered Oct 10 '19 at 10:40

11

Blow codes could help you...

Fetch Numbers:

return string.Concat(input.Where(char.IsNumber));

Fetch Letters:

return string.Concat(input.Where(char.IsLetter));

answered Oct 10 '19 at 10:40

Ali Rasoulian

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score 5 · Answer 4 · answered Nov 01 '09 at 14:25

5

var result = Regex.Replace("123- abcd33", @"[0-9\-]", string.Empty);

answered Nov 01 '09 at 14:25

Darin Dimitrov

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score 3 · Answer 5 · answered Sep 21 '18 at 09:40

3

As a string extension:

    public static string RemoveIntegers(this string input)
    {
        return Regex.Replace(input, @"[\d-]", string.Empty);
    }

Usage:

"My text 1232".RemoveIntegers(); // RETURNS "My text "

answered Sep 21 '18 at 09:40

Sgedda

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score 3 · Answer 6 · answered Jan 09 '22 at 02:32

Different methods and which is the fastest if you have 100000 iterations to do.

Code:

        Stopwatch sw = new Stopwatch();
        var maxIterations = 100000;

        Console.WriteLine(@"Removing digits from string: ""1mir1112211a3bc9"" with Total {0}x iterations ",maxIterations);
        Console.WriteLine("\nReplace Operations");
        sw.Start();
        var str = "1mir1112211a3bc9";
        for (int i = 1; i <= maxIterations; i++)
        {
            str = "1mir1112211a3bc9";

            str = str.Replace("1", "")
                     .Replace("2", "")
                     .Replace("3", "")
                     .Replace("4", "")
                     .Replace("5", "")
                     .Replace("6", "")
                     .Replace("7", "")
                     .Replace("8", "")
                     .Replace("9", "")
                     .Replace("0", "");
        }
        sw.Stop();
        
        Console.WriteLine("Finalstring: " + str);
        Console.WriteLine("Elapsed time: " + sw.Elapsed.TotalMilliseconds + " Milliseconds");

        sw.Reset();

        //list for and if 
        Console.WriteLine("\nList Operations:");
        sw.Start();
        var str2 = "1mir1112211a3bc9";
        var listOfchars = new List<char>();
        for (int i = 1; i <= maxIterations; i++)
        {
             str2 = "1mir1112211a3bc9";
            for (int j = 0; j < str2.Length; j++)
            {
                if( !(char.IsDigit(str2[j])))
                    listOfchars.Add(str2[j]);
            }
            str2 = new string(listOfchars.ToArray());
            listOfchars.Clear();
        }
        sw.Stop();
        Console.WriteLine("Finalstring: " + str2);
        Console.WriteLine("Elapsed time: " + sw.Elapsed.TotalMilliseconds + " Milliseconds");

           sw.Reset();
        //LINQ
        Console.WriteLine("\nLINQ Operations");

        sw.Start();
            var str1 = "1mir1112211a3bc9";
        for (int i = 1; i <= maxIterations; i++)
        {
            str1 = "1mir1112211a3bc9";
            str1 = String.Concat(str1.Where(c => c != '-' && (c < '0' || c > '9')) );
        }
        sw.Stop();

        Console.WriteLine("Finalstring: " + str1);
        Console.WriteLine("Elapsed time: " + sw.Elapsed.TotalMilliseconds + " Milliseconds");

        //Regex
        sw.Reset();
        
        Console.WriteLine("\nRegex Operations");

        sw.Start();
        var str3 = "1mir1112211a3bc9";
        for (int i = 1; i <= maxIterations; i++)
        {
            str3 = "1mir1112211a3bc9";
            str3 = Regex.Replace(str3, @"[\d-]", string.Empty);
        }
        sw.Stop();

        Console.WriteLine("Finalstring: " + str3);
        Console.WriteLine("Elapsed time: " + sw.Elapsed.TotalMilliseconds + " Milliseconds");

Here are the Results:

Removing digits from string: "1mir1112211a3bc9" with Total 100000x iterations

Replace Operations
Finalstring: mirabc
Elapsed time: 37,8307 Milliseconds

List Operations:
Finalstring: mirabc
Elapsed time: 16,7803 Milliseconds

LINQ Operations
Finalstring: mirabc
Elapsed time: 34,5803 Milliseconds

Regex Operations
Finalstring: mirabc
Elapsed time: 252,1907 Milliseconds

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score 2 · Answer 7 · answered Feb 05 '19 at 07:06

2

the best design is:

public static string RemoveIntegers(this string input)
    {
        return Regex.Replace(input, @"[\d-]", string.Empty);
    }

answered Feb 05 '19 at 07:06

Vitaly Yakel

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score 2 · Answer 8 · edited Dec 08 '20 at 08:26

2

text= re.sub('[0-9\n]',' ',text)

install regex in python which is re then do the following code.

edited Dec 08 '20 at 08:26

Roshin Raphel

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answered Dec 08 '20 at 08:24

Shubham Smiley

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How to remove numbers from string using Regex.Replace?

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