How can I strip punctuation from a string?

Question

For the hope-to-have-an-answer-in-30-seconds part of this question, I'm specifically looking for C#

But in the general case, what's the best way to strip punctuation in any language?

I should add: Ideally, the solutions won't require you to enumerate all the possible punctuation marks.

Different languages are, in fact, different, and I don't think there's an answer to the question you're asking. You could ask about specific languages, or what language would be best for that sort of manipulation. — David Thornley, Jun 17 '10 at 17:23

score 120 · Answer 1 · edited Aug 24 '11 at 12:33

120

new string(myCharCollection.Where(c => !char.IsPunctuation(c)).ToArray());

edited Aug 24 '11 at 12:33

Hath

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answered Jan 07 '09 at 19:09

GWLlosa

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1

Yup. It's powering the string operation I posted below. – Tom Ritter Jan 07 '09 at 19:24
10

LinQ never ceases to amaze me. – Dermot Jul 28 '12 at 02:57
Brilliant. Less is more. – Saeed Neamati Aug 21 '13 at 08:08
doesnt work on $ or ^, maybe more. I'm sticking with ^[a-zA-Z][a-zA-Z0-9]*$ – Stuart Dobson Mar 15 '14 at 09:21
PhoneNumberTextBox.Text = new string(PhoneNumberTextBox.Text.Where(c => !char.IsPunctuation(c)).ToArray()).Replace(" ",""); – dnennis Dec 25 '15 at 13:06
2

for $ or ^ u can use `!char.IsSymbol(c)` validation. just for the record – Razvan Dumitru Apr 17 '16 at 01:54

score 25 · Answer 2 · answered Jan 07 '09 at 19:51

25

Why not simply:

string s = "sxrdct?fvzguh,bij.";
var sb = new StringBuilder();

foreach (char c in s)
{
   if (!char.IsPunctuation(c))
      sb.Append(c);
}

s = sb.ToString();

The usage of RegEx is normally slower than simple char operations. And those LINQ operations look like overkill to me. And you can't use such code in .NET 2.0...

answered Jan 07 '09 at 19:51

Hades32

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Note that this approach also lets you replace punctuation with (for example) whitespace. Useful for tokenizing. – Jan 16 '14 at 21:19

Brian Low · Answer 3 · 2011-08-23T16:52:54.270

15

Describes intent, easiest to read (IMHO) and best performing:

 s = s.StripPunctuation();

to implement:

public static class StringExtension
{
    public static string StripPunctuation(this string s)
    {
        var sb = new StringBuilder();
        foreach (char c in s)
        {
            if (!char.IsPunctuation(c))
                sb.Append(c);
        }
        return sb.ToString();
    }
}

This is using Hades32's algorithm which was the best performing of the bunch posted.

edited Aug 23 '11 at 16:52

answered Jun 17 '10 at 16:57

Brian Low

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interesting tidbit: the following are not punctuation: $^+|<>= – Brian Low Jun 17 '10 at 17:07

Joachim Sauer · Answer 4 · 2009-01-07T19:16:10.153

14

Assuming "best" means "simplest" I suggest using something like this:

String stripped = input.replaceAll("\\p{Punct}+", "");

This example is for Java, but all sufficiently modern Regex engines should support this (or something similar).

Edit: the Unicode-Aware version would be this:

String stripped = input.replaceAll("\\p{P}+", "");

The first version only looks at punctuation characters contained in ASCII.

edited Jan 07 '09 at 19:16

answered Jan 07 '09 at 19:09

Joachim Sauer

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C# doesn't have the `Punct` class but it does have `P` – JProgrammer Dec 17 '17 at 21:28

Anton · Answer 5 · 2009-01-07T19:20:55.480

9

You can use the regex.replace method:

 replace(YourString, RegularExpressionWithPunctuationMarks, Empty String)

Since this returns a string, your method will look something like this:

 string s = Regex.Replace("Hello!?!?!?!", "[?!]", "");

You can replace "[?!]" with something more sophiticated if you want:

(\p{P})

This should find any punctuation.

edited Jan 07 '09 at 19:20

answered Jan 07 '09 at 19:12

Anton

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+1 for using a unicode character class. Concise, precise, and nice. – Tom Anderson Dec 14 '10 at 11:52

score 6 · Answer 6 · answered Sep 29 '11 at 13:26

6

This thread is so old, but I'd be remiss not to post a more elegant (IMO) solution.

string inputSansPunc = input.Where(c => !char.IsPunctuation(c)).Aggregate("", (current, c) => current + c);

It's LINQ sans WTF.

answered Sep 29 '11 at 13:26

Nick Vaccaro

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score 4 · Answer 7 · answered Jan 07 '09 at 19:23

4

Based off GWLlosa's idea, I was able to come up with the supremely ugly, but working:

string s = "cat!";
s = s.ToCharArray().ToList<char>()
      .Where<char>(x => !char.IsPunctuation(x))
      .Aggregate<char, string>(string.Empty, new Func<string, char, string>(
             delegate(string s, char c) { return s + c; }));

answered Jan 07 '09 at 19:23

Tom Ritter

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I know; right? I hobby of mine is committing sins against code in Linq. But please, by all means, make it better. – Tom Ritter Jan 07 '09 at 19:29
5

Please seek psychiatric help. – Tom Anderson Dec 14 '10 at 11:49
That's quadratic in the length in s; if you double the length, the code will be four times slower, because the + operator for string has to make a copy of the string :/ – Clément Jan 11 '13 at 22:49

score 2 · Answer 8 · answered Apr 05 '16 at 20:44

2

If you want to use this for tokenizing text you can use:

new string(myText.Select(c => char.IsPunctuation(c) ? ' ' : c).ToArray())

answered Apr 05 '16 at 20:44

Chris Marisic

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score 2 · Answer 9 · answered Jan 07 '09 at 19:08

2

The most braindead simple way of doing it would be using string.replace

The other way I would imagine is a regex.replace and have your regular expression with all the appropriate punctuation marks in it.

answered Jan 07 '09 at 19:08

TheTXI

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score 2 · Answer 10 · answered Jan 07 '09 at 19:39

2

Here's a slightly different approach using linq. I like AviewAnew's but this avoids the Aggregate

        string myStr = "Hello there..';,]';';., Get rid of Punction";

        var s = from ch in myStr
                where !Char.IsPunctuation(ch)
                select ch;

        var bytes = UnicodeEncoding.ASCII.GetBytes(s.ToArray());
        var stringResult = UnicodeEncoding.ASCII.GetString(bytes);

answered Jan 07 '09 at 19:39

JoshBerke

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Why the `IEnumerable` to array to bytes to string conversion, why not just `new String(s.ToArray())`? Or is that what new string will do under the hood anyway? – Chris Marisic Aug 24 '11 at 12:38

score 2 · Answer 11 · edited Apr 03 '20 at 19:03

For anyone who would like to do this via RegEx:

This code shows the full RegEx replace process and gives a sample Regex that only keeps letters, numbers, and spaces in a string - replacing ALL other characters with an empty string:

//Regex to remove all non-alphanumeric characters
System.Text.RegularExpressions.Regex TitleRegex = new 
System.Text.RegularExpressions.Regex("[^a-z0-9 ]+", 
System.Text.RegularExpressions.RegexOptions.IgnoreCase);

string ParsedString = TitleRegex.Replace(stringToParse, String.Empty);

return ParsedString;

Andrew · Answer 12 · 2015-04-18T22:14:39.933

I faced the same issue and was concerned about the performance impact of calling the IsPunctuation for every single check.

I found this post: http://www.dotnetperls.com/char-ispunctuation.

Accross the lines: char.IsPunctuation also handles Unicode on top of ASCII. The method matches a bunch of characters including control characters. By definiton, this method is heavy and expensive.

The bottom line is that I finally didn't go for it because of its performance impact on my ETL process.

I went for the custom implemetation of dotnetperls.

And jut FYI, here is some code deduced from the previous answers to get the list of all punctuation characters (excluding the control ones):

var punctuationCharacters = new List<char>();

        for (int i = char.MinValue; i <= char.MaxValue; i++)
        {
            var character = Convert.ToChar(i);

            if (char.IsPunctuation(character) && !char.IsControl(character))
            {
                punctuationCharacters.Add(character);
            }
        }

        var commaSeparatedValueOfPunctuationCharacters = string.Join("", punctuationCharacters);

        Console.WriteLine(commaSeparatedValueOfPunctuationCharacters);

Cheers, Andrew

score 0 · Answer 13 · answered Sep 03 '12 at 11:38

For long strings I use this:

var normalized = input
                .Where(c => !char.IsPunctuation(c))
                .Aggregate(new StringBuilder(),
                           (current, next) => current.Append(next), sb => sb.ToString());

performs much better than using string concatenations (though I agree it's less intuitive).

score 0 · Answer 14 · answered Dec 14 '10 at 11:42

0

$newstr=ereg_replace("[[:punct:]]",'',$oldstr);

answered Dec 14 '10 at 11:42

Ash Youssef

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1

score 0 · Answer 15 · answered Oct 26 '21 at 19:07

This is simple code for removing punctuation from strings given by the user

Import required library

    import string

Ask input from user in string format

    strs = str(input('Enter your string:'))

    for c in string.punctuation:
        strs= strs.replace(c,"")
    print(f"\n Your String without punctuation:{strs}")

score -1 · Answer 16 · answered May 11 '09 at 03:09

#include<string>
    #include<cctype>
    using namespace std;

    int main(int a, char* b[]){
    string strOne = "H,e.l/l!o W#o@r^l&d!!!";
    int punct_count = 0;

cout<<"before : "<<strOne<<endl;
for(string::size_type ix = 0 ;ix < strOne.size();++ix)   
{   
    if(ispunct(strOne[ix])) 
    {
            ++punct_count;  
            strOne.erase(ix,1); 
            ix--;
    }//if
}
    cout<<"after : "<<strOne<<endl;
                  return 0;
    }//main

How can I strip punctuation from a string?

16 Answers16

Import required library

Ask input from user in string format

Linked