title: Python Pandas, Name error using eval
body: <p>Can someone explain to me why i get NameError when eval is executing ? </p>
  
  <pre><code>toEval = ""
  for i in self.dtf.columns.values:
      if (self.lst.count(i) &gt; 0):
          toEval = toEval + "self.dtf[[" + i + "]].dropna(),"
  
  
  toEval = toEval[:len(toEval)-1]
  t = eval(toEval)
  </code></pre>