Regex Expression to extract coefficent of linear eq "2x-3y+0.5"

Question

I want to convert my eq to vector form so i need to extract the coefficient

r"[-+]?\d*\.\d+|\d+" I tried this but I am not able to get the "-" sign along with the integer. For 2x-3y+0 i am getting [2, 3, 0] but I need [2, -3, 0].

Answer 1

The expression in this answer is much better, since it does not capture the + for instance.

Being said that, my guess is your designed expression is also just fine, maybe we'd slightly modify that to:

[-+]?\d+\.\d+|[-+]?\d+

and it might likely work, since validation seems to be unnecessary.

Please see the demo and explanation here.

Test

import re

matches = re.finditer(r"[-+]?\d+\.\d+|[-+]?\d+", "-0.2x-0.73y-0.11z-0.2x-0.73y-0.11")
linear_eq_coeff=[]

for match in matches:
    linear_eq_coeff.append(match.group())
print linear_eq_coeff

Output

['-0.2', '-0.73', '-0.11', '-0.2', '-0.73', '-0.11']

Demo

const regex = /[-+]?\d+\.\d+|[-+]?\d+/gm;
const str = `-0.2x-0.73y-0.11z-0.2x-0.73y-0.11`;
let m;

arr = [];

while ((m = regex.exec(str)) !== null) {
 // This is necessary to avoid infinite loops with zero-width matches
 if (m.index === regex.lastIndex) {
  regex.lastIndex++;
 }

 // The result can be accessed through the `m`-variable.
 m.forEach((match, groupIndex) => {
  console.log(`Found match, group ${groupIndex}: ${match}`);
  arr.push(match);
 });
}

console.log(arr);

Advice

wjandrea advice is that:

Could simplify to [-+]?(\d*\.)?\d+

Answer 2

Just use a better regex.

>>>import re
>>>eqn = '2x-3y+0'
>>>re.findall(r'(-?(?:\d+(?:\.\d*)?|\.\d+))', eqn)
['2', '-3', '0']