title: regex that will check expression is valid arithmetic expression, for example 'a+b*c=d' is valid and accepted
body: <p>I made separate regexs for both but its not giving desired result. and it should work like check whole input string and return valid if its valid or invalid if its invalid.</p>
  
  <pre><code>import re
  identifiers = r'^[^\d\W]\w*\Z'
  operators = r'[\+\*\-\/=]'
  a = re.compile(identifiers, re.UNICODE)
  b = re.compile(operators, re.UNICODE)
  c = re.findall(a, 'a+b*c=d')
  d = re.findall(b, 'a+b*c=d')
  print c, 'identifiers'
  print d, 'operators'
  </code></pre>
  
  <p>Result of this snippet is</p>
  
  <pre><code>[ ] identifiers &amp;
  ['+', '*', '='] operators
  </code></pre>
  
  <p><strong>I want results like input string is valid or invalid by checking all characters of input string by both regex</strong></p>