Extract a Single (Unsigned) Integer from a String

Extract a single (unsigned) integer from a string

$str = 'In My Cart : 11 12 items';
preg_match_all('!\d+!', $str, $matches);
print_r($matches);

How to get only the number from a string?

filter_var

You can use filter_var and sanitize the string to only include integers.

$s = "Lesson 001: Complete";
echo filter_var($s, FILTER_SANITIZE_NUMBER_INT);

https://eval.in/309989

preg_match

You can use a regular expression to match only integers.

$s = "Lesson 001: Complete";
preg_match("/([0-9]+)/", $s, $matches);
echo $matches[1];

https://eval.in/309994

How can I extract an integer from within a string?

strtol doesn't find a number in a string. It converts the number at the beginning of the string. (It does skip whitespace, but nothing else.)

If you need to find where a number starts, you can use something like:

const char* nump = strpbrk(str, "0123456789");
if (nump == NULL) /* No number, handle error*/

(man strpbrk)

If your numbers might be signed, you'll need something a bit more sophisticated. One way is to do the above and then back up one character if the previous character is -. But watch out for the beginning of the string:

if ( nump != str && nump[-1] == '-') --nump;

Just putting - into the strpbrk argument would produce false matches on input like non-numeric7.

How to extract numbers from a string in Python?

If you only want to extract only positive integers, try the following:

>>> txt = "h3110 23 cat 444.4 rabbit 11 2 dog"
>>> [int(s) for s in txt.split() if s.isdigit()]
[23, 11, 2]

I would argue that this is better than the regex example because you don't need another module and it's more readable because you don't need to parse (and learn) the regex mini-language.

This will not recognize floats, negative integers, or integers in hexadecimal format. If you can't accept these limitations, jmnas's answer below will do the trick.

How Do I Take Out Only Numbers From A PHP String?

Correct variant will be:

$string = "Hello! 123 How Are You? 456";
$int = intval(preg_replace('/[^0-9]+/', '', $string), 10);

Can I extract only integers from each line in a string and save them in a list?

You can use str.isdigit() + str.join() (extract every character from the line and check it with str.isdigit(). Join every digit afterwards with str.join()):

s = """@ 544 000
* 600 000
‘7000..."""

for line in s.splitlines():
    print("".join(ch for ch in line if ch.isdigit()))

Prints:

544000
600000
7000

Or as a list:

numbers = [
    int("".join(ch for ch in line if ch.isdigit())) for line in s.splitlines()
]

EDIT: With added checks for lines not containing numbers:

numbers = [
    int(m)
    for line in s.splitlines()
    if (m := "".join(ch for ch in line if ch.isdigit())).isnumeric()
]

Extract multiple numbers from a string after a specific substring

You can use

(?:\G(?!\A)(?:[^\d\s]*200B)?|P:\h*)[^\d\s]*\K(?!200B)\d+

See the regex demo.

Details:

• (?:\G(?!\A)(?:[^\d\s]*200B)?|P:\h*) - either the end of the previous successful match and then any zero or more chars other than digits/whitespace and 200B, or P: and zero or more horizontal whitespaces
• [^\d\s]* - zero or more chars other than digits and whitespace
• \K - match reset operator that discards the text matched so far from the overall match memory buffer
• (?!200B)\d+ - one or more digits that are not starting the 200B char sequence.

See the PHP demo:

$text = 'H: 290‐314 P: 280‐301+330U+200B+331string‐305+351+338‐308+310 [2]';
if (preg_match_all('~(?:\G(?!\A)(?:[^\d\s]*200B)?|P:\h*)[^\d\s]*\K(?!200B)\d+~', $text, $matches)) {
    print_r($matches[0]);
}

Output:

Array
(
    [0] => 280
    [1] => 301
    [2] => 330
    [3] => 331
    [4] => 305
    [5] => 351
    [6] => 338
    [7] => 308
    [8] => 310
)

extract a number starting from some fix number from a given string using Regex expression

To match a certain number that starts with a fixed value and then has X amount of digits, you can use a basic pattern like

1901920100\d{3}

If you want to make sure there is no digit on both ends of the number, you can use

(?<!\d)1901920100\d{3}(?!\d)

See the regex demo #1 and demo #2.

Since the second regex contains lookbehind that is still not universally supported by all JS environments, you can re-write it as (?:^|\D)(1901920100\d{3})(?!\d) and grab Group 1 values.

JavaScript demos:

var strings = [ "1901920100153 abcx", "123 1901920100159 abcdf", "--> + - asdj 1901920100123 yuman" ];
var fixed_part = "1901920100";
var regex = new RegExp(fixed_part + "\\d{3}", "g");
for (var i=0; i<strings.length; i++) {
  console.log(strings[i], '=>', strings[i].match(regex));
}