title: Difference between `f=lambda t,y: -y` and `f=lambda y:-y`
body: <p>I would like to know whether there is a difference between defining the same function as given bellow: </p>
  
  <p><code>f=lambda t,y: -y</code>  and <code>f=lambda y:-y</code>  </p>
  
  <p>I'm learning how to solve ODEs in python and they are using this simple function in examples.<br>
  I get that <code>y</code> depends on <code>t</code> for the differential equation to make sense.<br>
  So when we define a function using lambda with <code>t</code> and <code>y</code> in the left hand side but the right hand side actually contains only <code>y</code>, does it says y depends on t? </p>