Detect Non Ascii Characters in a String

How do I detect non-ASCII characters in a string?

I found it more useful to detect if any character falls out of the list

if(preg_match('/[^\x20-\x7e]/', $string))

detect non ascii characters in a string

another possible way is to try to convert your string to ASCII and the try to detect all the generated non printable control characters which couldn't be converted

grepl("[[:cntrl:]]", stringi::stri_enc_toascii(x))
## [1]  TRUE FALSE  TRUE FALSE

Though it seems stringi has a built in function for this type of things too

stringi::stri_enc_mark(x)
# [1] "latin1" "ASCII"  "latin1" "ASCII"

How can I tell if a string has any non-ASCII characters in it?

Try with this regex. It tests for all ascii characters that have some meaning in a string, from space 32 to tilde 126:

var ascii = /^[ -~]+$/;

if ( !ascii.test( str ) ) {
  // string has non-ascii characters
}

Edit: with tabs and newlines:

/^[ -~\t\n\r]+$/;

How to detect non-ASCII character in Python?

# -*- coding: utf-8 -*-

import re

elements = [u'2', u'3', u'13', u'37\u201341', u'43', u'44', u'46']

for e in elements:
    if (re.sub('[ -~]', '', e)) != "":
        #do something here
        print "-"

re.sub('[ -~]', '', e) will strip out any valid ASCII characters in e (Specifically, replace any valid ASCII characters with ""), only non-ASCII characters of e are remained.

Hope this help

How to find out if there is any non ASCII character in a string with a file path

As suggested by several comments and highlighted by @CrisLuengo answer, we can iterate the characters looking for any in the upper bit set (live example):

#include <iostream>
#include <string>
#include <algorithm>

bool isASCII (const std::string& s)
{
    return !std::any_of(s.begin(), s.end(), [](char c) { 
        return static_cast<unsigned char>(c) > 127; 
    });
}

int main()
{
    std::string s1 { "C:\\Users\\myUser\\Downloads\\Hello my friend.pdf" };   
    std::string s2 { "C:\\Users\\myUser\\Downloads\\ü.pdf" };

    std::cout << std::boolalpha << isASCII(s1) << "\n";
    std::cout << std::boolalpha << isASCII(s2) << "\n";
}

true

false

Testing for Non ASCII character not working Java

If already have a String then iterate over each character and check if each character is in the range of printable ASCII characters space (0x20) to tilde (~).

  public static boolean isAscii(String v) {
      if (s != null && !s.isEmpty()) {
        for(char c : v.toCharArray()) {
            if (c < 0x20 || c > 0x7E) return false;
        }
      }
      return true;  
  }

May also want to review the Character static methods; e.g. isLetter(), isISOControl(), etc. See Reference.

In C#, how can I detect if a character is a non-ASCII character?

ASCII ranges from 0 - 127, so just check for that range:

char c = 'a';//or whatever char you have
bool isAscii = c < 128;

Check that a string contains only ASCII characters?

In Python 3.7 were added methods which do what you want:

str, bytes, and bytearray gained support for the new isascii() method, which can be used to test if a string or bytes contain only the ASCII characters.

Otherwise:

>>> all(ord(char) < 128 for char in 'string')
True
>>> all(ord(char) < 128 for char in 'строка')
False

Another version:

>>> def is_ascii(text):
    if isinstance(text, unicode):
        try:
            text.encode('ascii')
        except UnicodeEncodeError:
            return False
    else:
        try:
            text.decode('ascii')
        except UnicodeDecodeError:
            return False
    return True
... 
>>> is_ascii('text')
True
>>> is_ascii(u'text')
True
>>> is_ascii(u'text-строка')
False
>>> is_ascii('text-строка')
False
>>> is_ascii(u'text-строка'.encode('utf-8'))
False

How to check if a String contains only ASCII?

From Guava 19.0 onward, you may use:

boolean isAscii = CharMatcher.ascii().matchesAllOf(someString);

This uses the matchesAllOf(someString) method which relies on the factory method ascii() rather than the now deprecated ASCII singleton.

Here ASCII includes all ASCII characters including the non-printable characters lower than 0x20 (space) such as tabs, line-feed / return but also BEL with code 0x07 and DEL with code 0x7F.

This code incorrectly uses characters rather than code points, even if code points are indicated in the comments of earlier versions. Fortunately, the characters required to create code point with a value of U+010000 or over uses two surrogate characters with a value outside of the ASCII range. So the method still succeeds in testing for ASCII, even for strings containing emoji's.

For earlier Guava versions without the ascii() method you may write:

boolean isAscii = CharMatcher.ASCII.matchesAllOf(someString);