code: def fermi_energy_from_outcar( filename='OUTCAR' ):
      
      outcar = open(filename, "r").read()
      # returns a match object
      fermi_energy = re.search(r"E-fermi\s*:\s*([-.\d]*)", outcar)
      # take the first group - group(0) contains entire match
      fermi_energy = float(fermi_energy.group(1))
      return fermi_energy
docs: Finds and returns the fermi energy.
      Args:
      -filename: the name of the outcar file to be read
  
      Returns:
          (Float): The fermi energy as found in the OUTCAR