title: Python Loop counter returning 0
body: <p>I am coding a decision tree and a confusion matrix and I added loop counters to determine the run time of my code but it returns me 0.</p>
  <pre><code>L = 0
  def creatematrixnull(target):
      global L
      uniquetarget =unique(target)
      # we specifie the type to ease the plot
      dataframe=pd.DataFrame(columns=uniquetarget,index=uniquetarget, dtype='int32')
      for i in range(len(uniquetarget)):
          dataframe.iloc[i]=[0]*len(uniquetarget)
          L=L+1
      return dataframe 
      creatematrix=creatematrixnull(targettest)
  print(L)
  </code></pre>
  <p>This is an example of what I am talking about</p>