Regex for Python Variable Name

javascript

const regex = /^[a-zA-Z_][a-zA-Z0-9_]*$/;
const isValid = regex.test(value);

python

import re
pattern = r'^[a-zA-Z_][a-zA-Z0-9_]*$'
if re.match(pattern, value):
    print("valid")

ruby

pattern = /^[a-zA-Z_][a-zA-Z0-9_]*$/
if value =~ pattern
  puts "valid"
end

php

if (preg_match('/^[a-zA-Z_][a-zA-Z0-9_]*$/', $value)) {
    echo "valid";
}

java

String pattern = "^[a-zA-Z_][a-zA-Z0-9_]*$";
boolean isValid = value.matches(pattern);