title: How can I declare natural symbols with sympy?
body: <p>I know how to declare integer symbols:</p>
  
  <pre><code>from sympy import symbols
  
  
  a, b, c, m, n = symbols('a b c m n', Integer=True)
  </code></pre>
  
  <p>But I want that symbols are natural numbers without zero (strictly positive integers). How can I do it?
  Thanks</p>
  
  <p>Edit:</p>
  
  <p>If I calculate diophantine equation, it gives me negative solutions too, and i want only positive solutions:</p>
  
  <pre><code>from sympy.solvers.diophantine import diophantine
  from sympy import symbols
  
  
  a, b, c, m, n = symbols('a b c m n', integer=True, positive=True)
  
  a = n ** 2 - m ** 2
  b = 2 * n * m
  c = n ** 2 + m ** 2
  
  diof = diophantine(n ** 2 + m * n - 500)
  print(diof)
  </code></pre>
  
  <p>Look:
  {(121, 4), (499, -500), (95, -100), (499, 1), (-40, -10), (40, -50), (-499, 500), (-95, -5), (-40, 50), (-95, 100), (5, 20), (-5, 25), (-248, 250), (-499, -1), (121, -125), (5, -25), (-121, 125), (-5, -20), (-121, -4), (248, -250), (95, 5), (-248, -2), (40, 10), (248, 2)}</p>