title: Python - IndentationError: expected an indented block on a if
body: <p>I am new to python, so here is my problem.
  I get the error "IndentationError: expected an indented block" on y_list in line 31 -> after the first if.
  The file I load includes alot of numbers, and the idea is to skip the negative ones  in the socalled y_list.</p>
  
  <pre><code>filename = "data_5.dat" # this file can also be found in the sandbox folder 
  x_list = []
  y_list = []
  
  fp = open(filename)
  for line in fp:
      var1, var2  = line.split(",")    # here we wish to split the line using the ',' character
  
      # since we want them in numeric format we need to convert
      a = float(var1)
      b = float(var2)
  
      # put them into two lists
      x_list.append(a)
      y_list.append(b)
  
  fp.close()    # close the file
  
  
  x = x_list
  y = y_list
  
  I = 0.0
  L = 0.0
  
  for k in range(1, len(x)):
  if y_list&gt;0:
          y_list.append(y)
          I += y[k-1] * (x[k] - x[k-1])
  
  for k in range(1, len(x)):
  if y_list&gt;0:
          y_list.append(y)
          L += y[k] * (x[k] - x[k-1])
  
  print I
  print L
  print (I+L)/2
  </code></pre>