def show_instructions():
    """show command line instructions"""
    info = """
--------------------------
preprocess a single file
--------------------------

# write output to screen
> python preprocess.py [input csv file] [--old-format]

# write output to screen and file
> python preprocess.py [input csv file] [output file name] [--old-format]

OR

# test input and output files
> python preprocess.py test

"""
    print(info)
