How can I detect if a string is empty of characters?

Question

How do I determine if the string has any alpha character or not?

In other words, if the string has only spaces in it how do I treat it as an Empty string?

Answer 1

Try:

if the_string.replace(" ", "") == "":
    the_string = ""

If your language supports it, using "trim", "strip" or "chomp" to remove leading/trailing whitespace could be good too...

edit: Of course, regular expressions could solve this problem too: the_string.match("[^\s]")... Or a custom function... Or any number of things.

edit: In Caml:

let rec empty_or_space = fun
      [] -> true
    | (x::xs) -> x == ` ` and empty_or_space xs;;

edit: As requested, in LOLPYTHON:

BTW OHAI
SO IM LIKE EMPTY WIT S OK?
    LOL IZ S EMPTIE? DUZ IT HAZ UNWHITESPACE CHAREZ /LOL
    IZ S KINDA LIKE ""?
        U TAKE YEAH

    IZ S LOOK AT EASTERBUNNY OK KINDA NOT LIKE " "?
        U TAKE MEH

    U TAKE EMPTY WIT S OWN __getslice__ WIT CHEEZBURGER AND BIGNESS S OK OK

Answer 2

In C# you should use String.IsNullOrEmpty.

To treat it as an empty string you can just use "" or string.Empty; To check if its empty there is a .Trim function.

Answer 3

C++

#include <string>

bool isEmptyOrBlank(const std::string& str)
{
   int len = str.size();
   if(len == 0) { return true; }

   for(int i=0;i<len;++i)
   {
       if(str[i] != ' ') { return false; }
   }
   return true;
}

C

#include <string.h>

int isEmptyOrBlank(const char* str)
{
  int i;
  int len;

  len = strlen(str);

  //String has no characters
  if(len == 0) { return 1; }

  for(i=0;i<len;++i)
  {
     if(str[i] != ' ') { return 0; }
  }

  return 1;
}

Java

boolean isEmptyOrBlank(String str)
{
  int len = str.length();
  if(len == 0) { return true; }

  for (int i = 0; i < len; ++i)
  {
    if (str.charAt(i) != ' ')  { return false; }
  }

  return true;
}

You get the idea, you can do something similar in any language.

Answer 4

if you talking about .Net(C# or vb), then you can Trim() it to remove white spaces.

Answer 5

if (s =~ /^\w*$/)

should work, as long as you're using Perl.

Anybody got a LOLCODE version?

Answer 6

If you are using .NET, then the string type has a .Trim() method that strips leading and trailing spaces.

Answer 7

If you really want to treat a string that only contains spaces as an empty string (which it isn't but that's a different story) just use whatever stripping method your language of choice provides (string.lstrip() and string.rstrip() in Python for example) and check if the resulting string has the length 0.

Answer 8

The canonical method, regardless of language, is to trim the string (trim functions remove whitespace at the beginning and end of a string) and compare the result to the empty string:

if (trim(myString) == "") {
    // string contains no letters, numbers, or punctuation
}

Not all languages have a native trim function, however. Here's a good, general-purpose one for JavaScript, since I haven't seen a JS example yet:

function trim(str) {
    return str.replace(/^\\s+|\\s+$/g, "");
}

(Check out Steven Levithan's post about JavaScript trim functions for an in-depth comparison.)

Alternatively, you can use a regular expression to test "emptiness":

if (/^\s*$/.test(str)) {
    // string contains no letters, numbers, or punctuation
}

Again, not all languages natively support regular expressions. Check your language documentation.

Answer 9

The kind people a Microsoft added this method

string myStr = "    ";    
string.IsNullOrWhiteSpace(myStr)

This will do the job if you are using .net.

string myStr = "    ";    
string.IsNullOrEmpty(myStr.Trim()));

If you are using .net 3.0 or above then you might like to create an extension method for this that you can use with any string.

namespace StringExtensions
{
    public static class StringExtensionsClass
    {
        public static string IsWhiteSpace(this string s)
        {
            return string.IsNullOrEmpty(s.Trim()));
        }
    }
}

You can then use this like so

string myStr = "    ";
if (myStr.IsWhiteSpace())
    Console.Write("It just whitespace");

Hope that this is what you are after.

Answer 10

a = ' '
b = a if a.replace(' ','') else a.replace(' ','')

Answer 11

C#:

Empty means (MSDN) The value of this field is the zero-length string, "".

Therefor if you have spaces it will not be empty

private bool IsEmtpyOrContainsAllSpaces(String text)
        {
            int count = 0;
            foreach (char c in text)
            {
                if (c == ' ')
                {
                    count++;
                }
            }
            return (count == text.Length);
        }