6.11. Numbers with Thousand Separators
Problem
You want to match numbers that use the comma as the thousand separator and the dot as the decimal separator.
Solution
Mandatory integer and fraction:
^[0-9]{1,3}(,[0-9]{3})*\.[0-9]+$
Regex options: None |
Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
Mandatory integer and optional fraction. Decimal dot must be omitted if the fraction is omitted.
^[0-9]{1,3}(,[0-9]{3})*(\.[0-9]+)?$
Regex options: None |
Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
Optional integer and optional fraction. Decimal dot must be omitted if the fraction is omitted.
^([0-9]{1,3}(,[0-9]{3})*(\.[0-9]+)?|\.[0-9]+)$
Regex options: None |
Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
The preceding regex, edited to find the number in a larger body of text:
\b[0-9]{1,3}(,[0-9]{3})*(\.[0-9]+)?\b|\.[0-9]+\b
Regex options: None |
Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
Discussion
Since these are all regular expressions for matching
floating-point numbers, they use the same techniques as the previous
recipe. The only difference is that instead of simply matching the
integer part with ‹[0-9]+
›, we now use ‹[0-9]{1,3}(,[0-9]{3})*
›. This regular expression
matches between 1 and 3 digits, followed by zero or more groups that
consist of a comma and 3 digits.
We cannot use ‹[0-9]{0,3}(,[0-9]{3})*
› to make the integer part
optional, because that would match numbers with a leading comma (e.g.,
,123
). It’s the same trap of making ...
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