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
– jle

2009-11-01 14:23:15 +00:00
Commented Nov 1, 2009 at 14:23 — jle
– jle, Commented Nov 1, 2009 at 14:23

Noldorin · Accepted Answer · 2009-11-01 14:23:48Z

170

Try the following:

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

The \d identifier simply matches any digit character.

answered Nov 1, 2009 at 14:23

Noldorin

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2 Comments

Aaron Franke Over a year ago

What is the purpose of the dash? I know it's used for ranges, but there's nothing at the right?

volkit Over a year ago

Purpose is to remove it together with numbers. See input/output example in question.

Guffa · Accepted Answer · 2009-11-01 14:54:11Z

29

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 1, 2009 at 14:54

Guffa

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5 Comments

Guffa Over a year ago

@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.

Arnold Wiersma Over a year ago

@Guffa Do you know how this scales? Lets say on 50k records should I go for RegEx?

Guffa Over a year ago

@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.

Skorunka František Over a year ago

alternatively new string(text.Where(char.IsLetter).ToArray());

Uke Over a year ago

@SkorunkaFrantišek, the problem here is that this also trims the string

Ali Rasoulian · Accepted Answer · 2019-10-10 10:40:03Z

13

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, 2019 at 10:40

Ali Rasoulian

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Comments

Darin Dimitrov · Accepted Answer · 2009-11-01 14:25:04Z

6

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

answered Nov 1, 2009 at 14:25

Darin Dimitrov

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Comments

amehmood · Accepted Answer · 2022-01-09 02:32:08Z

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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I liked seeing the comparison between the methods. I will still use the Regex approach for readability and because I only have a few iterations to do, but it is still good to know how much slower the Regex is compared to the other methods.

Sgedda · Accepted Answer · 2018-09-21 09:40:06Z

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, 2018 at 9:40

Sgedda

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Comments

Vitaly Yakel · Accepted Answer · 2019-02-05 07:06:51Z

2

the best design is:

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

answered Feb 5, 2019 at 7:06

Vitaly Yakel

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Comments

Roshin Raphel · Accepted Answer · 2020-12-08 08:26:21Z

2

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

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

edited Dec 8, 2020 at 8:26

Roshin Raphel

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answered Dec 8, 2020 at 8:24

Shubham Smiley

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Comments

Chris Raisin · Accepted Answer · 2024-05-29 09:52:17Z

After seeing how much faster a list operation is in replacements, I created a user Class (in VB.Net) named "CKRReplace". The "CKR" prepend is my initials, rather than calling it simply "Replace" (which is used so often elsewhere in VB Code).

    Public Class CKRReplace
      Public Function AllNumbers(strSource As String, _
                                 Optional strReplace As String = "") _
                                 As String
        strSource = strSource.Replace("1", strReplace) _
        .Replace("2", strReplace) _
        .Replace("3", strReplace) _
        .Replace("4", strReplace) _
        .Replace("5", strReplace) _
        .Replace("6", strReplace) _
        .Replace("7", strReplace) _
        .Replace("8", strReplace) _
        .Replace("9", strReplace) _
        .Replace("0", strReplace)
        Return strSource
    End Function
  End Class

Calls to the code to remove all numbers would be from the string "1mir1112211a3bc9" would be something like (again in VB.Net): Dim oReplace as new CKRReplace Dim str1 as string = "1mir1112211a3bc9" oReplace.AllNumbers(str1,"")

The second parameter passed to the oReplace object is not really required since that parameter defaults to "", but I included it for clarity.

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