RegEx to match comma separated numbers with optional decimal part - regex

Question

I've a regex that matches comma separated numbers with an optional two digit decimal part in a given multiline text.
/(?<=\s|^)\d{1,3}(,\d{3})*(\.\d{2})?(?=\s|$)/m
It matches strings like 1, 12, 12.34, 12,345.67 etc successfully. How can I modify it to match a number with only the decimal part like .23?
EDIT: Just to clarify - I would like to modify the regex so that it matches 12, 12.34 and .34
And I am looking for 'stand alone' valid numbers. i.e., number-strings whose boundaries are either white space or start/end of line/string.

Answer 1

This:
\d{1,3}(,\d{3})*(\.\d\d)?|\.\d\d
matches all of the following numbers:
1
12
.99
12.34
12,345.67
999,999,999,999,999.99
If you want to exclude numbers like 123a (street addresses for example), or 123.123 (numbers with more than 2 digits after the decimal point), try:
(?<=\s|^)(\d{1,3}(,\d{3})*(\.\d\d)?|\.\d\d)(?=\s|$)
A little demo (I guessed you're using PHP):
$text = "666a 1 fd 12 dfsa .99 fds 12.34 dfs 12,345.67 er 666.666 er 999,999,999,999,999.99";
$number_regex = "/(?<=\s|^)(?:\d{1,3}(?:,\d{3})*(?:\.\d\d)?|\.\d\d)(?=\s|$)/";
if(preg_match_all($number_regex, $text, $matches)) {
print_r($matches);
}
which will output:
Array
(
[0] => Array
(
[0] => 1
[1] => 12
[2] => .99
[3] => 12.34
[4] => 12,345.67
[5] => 999,999,999,999,999.99
)
)
Note that it ignores the strings 666a and 666.666

Answer 2

/(?<=\s|^)(\d{1,3}(,\d{3})*(\.\d{2})?|\.(\d{2}))(?=\s|$)/m
Or taking into account some countries where . is used as a thousand seperator, and , is used as a decimal seperator
/(?<=\s|^)(\d{1,3}(,\d{3})*(\.\d{2})?|\d{1,3}(\.\d{3})*(,\d{2})?|\.(\d{2})|,(\d{2}))(?=\s|$)/m
Insane Regex for Internationalisation
/((?<=\s)|(?<=^))(((\d{1,3})((,\d{3})|(\.\d{3}))*(((?<=(,\d{3}))(\.\d{2}))|((?<=(\.\d{3}))(,\d{2}))|((?<!((,\d{3})|(\.\d{3})))([\.,]\d{2}))))|([\.,]\d{2}))(?=\s|$)/m
Matches
14.23
14,23
114,114,114.23
114.114.114,23
Doesn't match
14.
114,114,114,23
114.114.144.23
,
.
<empty line>

Answer 3

This answer treats with this question more comprehensively.

Answer 4

(#"^((([0-9]+)(.([0-9]+))?)(\,(([0-9]+)(.([0-9]+))?))*)$")
This works for comma separated whole number or comma separated decimal numbers.
Example:
Happy scenarios:
case 1) 9,10
case 2) 10.1,11,12,15,15.2
case 3) 9.8
case 4) 9
Sad scenarios:
case 1) 2..7
case 2) 2,,7
case 3) 2.
case 4) 7,
case 5) ,
case 6) .
case 7) .2
case 8) ,2