Numbersflags: g

Float / Scientific Number

Match floating-point and scientific-notation numbers including `1.5`, `.25`, `1e10`, `-3.14E-2`.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("[-+]?(?:\\d+\\.?\\d*|\\.\\d+)(?:[eE][-+]?\\d+)?", "g");
const input = "h = 6.626e-34, c = 3e8, alpha = .007";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

Python (re) code

pyPython

import re

pattern = re.compile(r"[-+]?(?:\d+\.?\d*|\.\d+)(?:[eE][-+]?\d+)?")
input_text = "h = 6.626e-34, c = 3e8, alpha = .007"
for m in pattern.finditer(input_text):
    print(m.group(0))

Stdlib `re` module — no third-party dependency. Works on Python 3.6+.

Go (RE2) code

goGo

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`[-+]?(?:\d+\.?\d*|\.\d+)(?:[eE][-+]?\d+)?`)
	input := `h = 6.626e-34, c = 3e8, alpha = .007`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.

Pattern

regexengine-agnostic

[-+]?(?:\d+\.?\d*|\.\d+)(?:[eE][-+]?\d+)?   (flags: g)

Raw source: [-+]?(?:\d+\.?\d*|\.\d+)(?:[eE][-+]?\d+)?

How it works

[-+]? matches an optional sign. (?:\d+\.?\d*|\.\d+) matches the mantissa as either digits-with-optional-decimal or decimal-with-trailing-digits. (?:[eE][-+]?\d+)? matches the optional exponent. Covers most real-number literals you'll encounter in source or data.