title: Trying to create a function that returns a key of "strings" based on a value of "integers" from a dictionary
body: <pre class="lang-py prettyprint-override"><code>data = Sig_List.readlines()
  N, E = [], []
  for line in data:
      values = [str(s) for s in line.split()]
      N.append(values[0])
      E.append(values[1])
  
      Sig1 = dict(zip(N,E))
      Sig1={'Atg4a': '1.0241564267288767', 'Mast2': '-1.0014505579938486',...}
         
  def up1(Sig1):
      for key, value in Sig1.items():
          if value &gt;0:
              x=list(key)
      
  up1(Sig1)
  </code></pre>
  <p>Trying to input a list of gene names with a FC value and then generate sublists of up down genes that can be combined to make a venn diagram amongst different experiments. Having trouble defining a conditional function that returns only gene names based on wether they are up or down. Any help or suggestions would be appreciated.</p>