title: AttributeError: partially initialized module 'sympy' has no attribute 'S' (most likely due to a circular import)
body: <p>This is my code</p>
  <pre><code>x,t = sympy.S('x,t')
  
  def dawson(i):
      x = i
      expression = sympy.E**(-x**2) * sympy.integrate(sympy.E**(t**2),t,0,x)
      return sympy.lamdify(expression)
  </code></pre>
  <p>but I get that weird error when I execute it, and this is the first time this is happening. Why is sympy <em>partially</em> initialized and what does a circular import mean here?</p>